This error occurs if a drive BitTorrent is trying to access does not exist, or is missing. This most frequently occurs if a drive letter has changed, or if the data BitTorrent was looking for was located in a removable drive that is no longer in the computer. To resolve the issue, make sure the paths BitTorrent is trying to use are all existent. This means that all torrent jobs should not have their Save As field set to a directory on some non-existent drive letter. The same thing applies to the Directories preferences.
If a torrent job is using a drive letter that no longer exists, make sure you set the download location for the job.
This means that BitTorrent was unable to add itself as an exception to the Windows Firewall using the standard Windows Firewall API. This occurs when Windows Firewall is disabled or not present, or that you are using an operating system that does not support the API (operating systems older than Windows XP SP2). The error is non-fatal, and can be safely ignored. If you want BitTorrent to stop trying to add itself to the firewall exceptions list every time it starts, then you can disable the Add BitTorrent to Windows Firewall exceptions option in the Preferences. If another firewall is present, you will still need to configure it properly to allow BitTorrent to access the Internet.
This means that BitTorrent was unable to map (forward) the port with NAT-PMP. If you have a green status light in the status bar, or the Setup Guide's port checker verifies that the port is open, then you can safely ignore this error. If otherwise, you'll need to manually forward the port in your router. If you want BitTorrent to stop trying to map its listening port via NAT-PMP every time it starts, then you can disable the Enable NAT-PMP port mapping option in the Preferences.
This means that BitTorrent was unable to map (forward) the port with UPnP. If you have a green status light in the status bar, or the Setup Guide's port checker verifies that the port is open, then you can safely ignore this error. If otherwise, you'll need to manually forward the port in your router. If you want BitTorrent to stop trying to map its listening port via UPnP every time it starts, then you can disable the Enable UPnP port mapping option in the Preferences.
This means that the disk was not able to keep up with the read/write speeds. To fix this, you should try tweaking your Disk Cache settings in the Preferences. Note that disk overloads may also occur if the device you are writing to or reading from is inherently slow by design (USB hard drives, for example). In such cases, tweaking the cache settings may help, but it isn't guaranteed to work.
If you get this error message when you add a new torrent job, consider it normal due to a design limitation in BitTorrent (which should be fixed in the future). You can ignore the message, as it does not actually indicate any real disk overload. The message will disappear after a short amount of time.
This means that an error occurred the last time BitTorrent was run. Since BitTorrent does not remember error messages, no error is specified. Try resuming the torrent job, or forcing a re-check to see if any error occurs again.
Make sure you are not using a misconfigured incompatible software that can cause file access issues. If you are not, then make sure you have the right credentials to be using the target file and/or (containing) directory.
On some systems, Windows Explorer may attempt to preview media files when you are browsing the containing directory for the files. If this happens while BitTorrent is attempting to write to the file, then BitTorrent won't be able to access the file, and accordingly, it will throw this error message. To prevent this from happening, make sure you don't view the folder in "Thumbnail" or "Filmstrip" mode. Additionally, you may want to consider unregistering the shell media file property extractor in Windows by visiting "Start" > "Run" (or by pressing Windows+R on the keyboard), typing regsvr32 /u shmedia.dll into the "Open" field, and pressing "OK."
In the torrent job status, I get "Error: Data Error (cyclic redundancy check)" and BitTorrent halts the torrent job
This error is not an error generated by BitTorrent, but rather, an error it receives from the hard drive. The error indicates that the hard drive was unable to read or write the data because the sectors are faulty, or are about to die. Cyclic redundancy check (CRC) errors are often signs of possible future disk corruption. Running chkdsk might help fix the problem, but stronger recovery tools (such as SpinRite) may be required (assuming the disk is at all repairable).
This error may occur when you remove or rename files from a torrent job. If this is the case, try to re-add or rename the files back, or force a re-check on the torrent job.
In the torrent job status, I get "Error: The requested operation could not be completed due to a file system limitation" and BitTorrent halts the torrent job
This error occurs because of a problem with the way Windows Vista handles sparse files and NTFS compressed. When a sparse or compressed file reaches this (currently unspecified) limitation, all writes to the file will fail. The only way around this is to make a copy of the file, delete the existing (sparse/compressed) file, and replace the deleted file with the copy. It is recommended that you disable diskio.sparse_files if you are running Windows Vista. If you would like BitTorrent to not fully allocate a file upon write while using Windows Vista, use bt.compact_allocation instead.
In the torrent job status, I get "Error: Not enough free space on disk" when I have more than enough free space
This error occurs only on drives or partitions formatted to FAT32 because files greater than 4 GiB cannot be created on FAT32 partitions. The only fix is to convert the drive or partition to NTFS, or use another drive or partition that is already using NTFS.
To convert a drive to NTFS, read Microsoft's knowledge base article KB307881.
The cause of the error message is currently unknown, though it is being looked into. There is no workaround apart from not using selective file downloading on these operating systems if you receive the error. The error should not happen again if you simply resume the torrent job.
In the torrent job status, I get "Error: The process cannot access the file because it is being used by another process" and BitTorrent halts the torrent job
See the question regarding Error: Access Denied.
In the torrent job status, I get "Error: The requested operation cannot be performed on a file with a user-mapped section open" and BitTorrent halts the torrent job
Make sure you are not using a misconfigured incompatible software that can cause file access issues.
In the torrent job status, I get "Error: The system cannot find the path specified" and BitTorrent halts the torrent job
This problem may be caused by a limitation in Windows with path lengths. Windows limits the maximum path length (including filenames) to 255 characters. Try saving the torrent contents to a location closer to the drive's root, such as C:\Downloads\.
Check to make sure you don't have an incompatible software installed. Previous reports on this error message indicate that BitDefender Firewall can cause such issues. There is no known way to fix the issue other than to uninstall the firewall (and replace it with another one if necessary).
If you are not using any software firewall, make sure you have the latest drivers installed for your network card, since this problem may well be caused by buggy drivers. It may also occur if your network gets physically disconnected (like if the network cable is disconnected, or if your modem or router shuts off).
In the tracker status, I get "An operation on a socket could not be performed because the system lacked sufficient buffer space or because a queue was full" and BitTorrent halts
Check to make sure you don't have an incompatible software installed. Previous reports on this error message indicate that Norton GoBack can cause such issues. Updating the application or uninstalling it entirely should solve the problem.
There is a Windows Registry entry in Windows 2000/XP/2003 that can cause this error. Read Microsoft's knowledge base article KB196271 for further details.
This error can also be a symptom of improper configuration. Check this FAQ entry regarding interrupted connections, as the suggestions may solve this problem.
In general, this error has manifested itself in cases where the user's ISP is interfering with BitTorrent tracker communication. Consult the Bad ISPs list on AzureusWiki to check if your ISP is known to interfere with BitTorrent traffic.