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If you find your µTorrent process uses a huge amount of memory abnormally, or steadily increasing for no reason (especially with DHT on), and you use the NVIDIA integrated firewall, you MUST UNINSTALL THE FIREWALL. Disabling it will not work! The firewall has a serious bug (which has NOT been fixed to this date) that causes many programs to leak large amounts of memory. It is NOT a µTorrent bug. There is no fix for this, you MUST uninstall the NVIDIA Firewall. However, the latest version of the NVIDIA Firewall (bundled with the newest nForce drivers) appears to fix this problem. µTorrent still presents the warning dialog, but this will be rectified in the next version.
Sources for this info: http://forum.emule-project.net/lofiversion/index.php/t86089.html
http://forums.nvidia.com/lofiversion/index.php?t2682.html
This is a bug with BitDefender, NOT µTorrent. Unfortunately, disabling this software will not work, so you must uninstall BitDefender to fix the problem. Please uninstall it and use something else, there is no fix for this.
If you experience this problem and are NOT using BitDefender, please try uninstalling (not disabling) the firewall. If it works, please inform us on the µTorrent forums, making sure to tell us which firewall caused the problem.
If you are not using any firewall, make sure you have the latest drivers for your network card, since this problem can be caused by buggy NICs. It can also be caused if your network gets physically disconnected or if the modem/router shuts off.
Stardock's ObjectDock can sometimes cause µTorrent's and various other programs' windows to apparently freeze and stop updating. The programs themselves still function, but their GUIs will no longer refresh. Please uninstall ObjectDock and use an alternative dock program, such as YzDock, since there is no fix for this bug if it happens to you. This is NOT a µTorrent bug.
You should no longer experience this with the latest version of µTorrent.
Error: Access Denied can be caused by numerous things. The most common causes seem to be Google and MSN Desktop. A possible fix is turn off the indexing feature, or to uninstall them. Excluding the download folders from indexing should work.
Another fix is to turn off diskio.flush_files, but you will lose the benefit of flush files (diskio.flush_files makes µTorrent close file handles every minute. This helps reduce the effect of Windows managing the system cache badly). Since flush files closes the handle every minute, Google/MSN Desktop try to open the file every minute, and this prevents µTorrent from writing.
The best solution is to uninstall Google/MSN Desktop.
WinZIP Quickfind has the same effect as Google/MSN Desktop. It must be disabled.
Roxio Media Manager and Nero Scout both do the same. They are installed by default when installing Roxio's and Nero's burning software, respectively. They must be disabled, or uninstalled.
It is possible that an anti-virus' real-time scanner may cause this, but there is no known AV that causes this error. If it does, the same fixes for Google/MSN Desktop apply (exclude the folder(s), uninstall the AV/disable the real-time scanner, or turn off flush files).
AVG7 may cause this, it seems to think that some files are a JPEG exploit (a false positive), and it attempts to quarantine them.
A third possibility is that you are viewing the folder while it's downloading, and Explorer is set to thumbnail mode. If this is the case, Explorer would try to access these files while viewing the folder in Thumbnail mode, and lock out µTorrent from writing. The solution is to not view the folder until the download is finished, don't use Thumbnail mode, or turn off flush files.
It's also possible that Explorer is trying to read the media files (MP3, AVI and so on) in the folder to make thumbnails, show you information about them, or preview them. You can unregister the media indexer (Start -> Run -> regsvr32 /u shmedia.dll ), and/or unregister the image indexer (Start -> Run -> regsvr32 /u shimgvw.dll ) as an alternative for either case, not view the folder, or turn off flush files.
A fourth possibility is that you set the files to read-only, which would prevent µTorrent from writing. This only affects downloading; µTorrent can seed files that are set to read-only. However, if the error appears when trying to seed, it may mean that the original files are damaged and are failing the hash check.
This can be caused by Avast!'s P2P shield, which scans P2P apps. Disabling this option will fix your problem.
Here's step-by-step instructions on disabling the P2P shield (thanks to scarface_666):
Alternatively, Avast! has a Customize option button besides the Sensitivity slider bar. You can exclude programs from the P2P shield in there. Excluding utorrent.exe may also solve the problem.
Spyware Doctor 5 causes µTorrent to freeze when installed. The only fix is to uninstall it, or roll back to version 4 of Spyware Doctor.
Kerio Personal Firewall / Sunbelt Personal Firewall has a bug where it uses 100% CPU and may cause your connection to drop when using µTorrent.
The fix for this is to:
The following note does NOT apply to WRT54G/GS v5 and up! Use the latest official firmware (1.00.9+) with those, they do not suffer from this specific problem (though they do suffer from different problems).
The default firmware for Linksys (and all replacement firmwares except for the latest DD-WRT and HyperWRT Thibor) have a severe problem where they track old connections for FIVE days, which causes the router to hang when using P2P apps, or any software that generates a lot of connections. DHT only aggravates the situation because of the number of connections it generates.
Linksys has yet to address this issue, but there is a fix. If you use alternative firmware, you can put in a start-up script to fix this problem. DD-WRT and HyperWRT support custom start-up scripts.
I am not responsible if you screw up your router, so you do this at your own risk. This page has instructions on recovering a bricked router.
If you experience any strange issues or performance problems, clear your NVRAM, and if all else fails, try changing firmwares (but make sure you clear the NVRAM afterwards!)
You should avoid upgrading over a wireless connection, since the connection may drop out and brick the router.
To upgrade the firmware follow the instructions on the download section of Thibor's page if flashing to HyperWRT Thibor, and make sure you download the correct firmware version for your router!
Neither DD-WRT v23+ nor DD-WRT Thibor14+ require these steps, but older versions of HyperWRT tofu/Thibor do. If you are on an old DD-WRT, you MUST upgrade to v23 SP2 or later.
echo 1 > /proc/sys/net/ipv4/icmp_echo_ignore_broadcasts
echo 1 > /proc/sys/net/ipv4/icmp_ignore_bogus_error_responses
echo "600 1800 120 60 120 120 10 60 30 120" > /proc/sys/net/ipv4/ip_conntrack_tcp_timeouts
To upgrade to DD-WRT, follow the instructions on this page. WRT54G v4 Installation Tutorial.
For a detailed explanation of what these settings do, see Router Slowdown @ DD-WRT Wiki
Remember, I am not responsible if you screw up your router, so it's your problem if something goes wrong. However, if something does go wrong, this page has instructions on recovering a bricked ("dead") router.
If you require further assistance with either firmware, please visit HyperWRT.org (the main site does not have the latest builds however), HyperWRT Forum's Advanced Help Section, DD-WRT.org, and DD-WRT's Wiki.
Please do not ask for help with these firmwares on the µTorrent forums.
Norton AntiVirus will continually prompt you to permit or block µTorrent regardless of if you hit Permit or Block. This is caused by NAV's Worm Protection.
Another solution is to simply turn off the Worm Protection, since it does not help much, or to uninstall Norton and get a better AntiVirus, since Norton has been shown to miss many worms, and to be working with companies against protecting your PC from rootkits.
The latest version of Norton Internet Security 2006 and Norton AntiVirus 2006 SHOULD fix this issue.
Norton GoBack appears to cause this problem (and it can manifest itself with other clients). Specifically, it is the component GBTray.exe of Norton GoBack that causes this. You can either close GBTray.exe before running µTorrent and keep it closed during the entire session (GoBack appears to still work with it closed), or disable Norton GoBack. Updating to version 4.1 will fix this issue.
There is also a registry setting in Windows 2000/XP/2003 that can cause this error. Read this Microsoft KB article for further information and a fix. KB196271
This can also be caused if you have your net.max_halfopen set to value other than 8, and have not patched TCPIP.SYS using the EventID 4226 Patcher" (XP SP2 and 2003 only). If you have patched it, check it again, because it gets reverted occasionally by Windows patches.
List of routers that have problems with Azureus (and µTorrent), if you have one of those... either try the solution specified with it (if there is any), update the firmware or get a new one. If your router or modem freezes/reboots, you should turn off IP resolving, DHT, and/or reduce the number of connections to try to remedy the problem, even if it's not on this list.
The following modems/routers have known problems with too many global connections, limiting them to 200 or less should fix the problems:
Sourced from (with some modifications): Bad routers - AzureusWiki
If you gets lots of hash fails on your torrents with a D-Link router, make sure DMZ mode isn't on. The DMZ mode in this router (called game mode) mangles packets and causes corruption like this, preventing you from completing a torrent.
This can be caused by severe problems with McAfee Firewall and Norman Personal Firewall. The only solution is to uninstall the firewall and use another.
This can also be caused by a bug with SpamPal (other programs exhibit the same behavior when this is installed). The only fix is to uninstall it, or use SpamPal 1.594.
Cybersitter can also cause this, only an uninstall will fix it.
If you don't have this firewall and still get high CPU use (either utorrent.exe, or an unseen process), run Sysinternals Process Explorer and see if the DPCs are using significant amounts of CPU. If this is the case, it may be buggy software (most likely not µTorrent), buggy drivers, or faulty hardware. You can run Microsoft's RATTV3 to find out the cause of the DPC. The log files from it are stored in C:\WINDOWS\system32\LogFiles\RATTV3
You can also check the properties of the µTorrent process in Process Explorer, click on the Threads tab, and see what DLLs are hooked into the process to find out what's causing the issue. Seeing mswsock.dll is normal.
V-Com's software causes µTorrent (among other software) to crash. You must uninstall V-Com's software.
Norman Personal Firewall and McAfee Firewall can also cause this, you must uninstall them if you experience crashes.
Cybersitter can also cause this, only an uninstall will fix it.
For more applications that are known to cause crashes and possible workarounds, consult this forum thread.
Norton AntiVirus and McAfee Anti-virus have a "Buffer overrun protection" option in their settings. This must be disabled to fix the issue.