Missing datachannel.dll

Unfortunately, BitTorrent is known to be used heavily to download illegal media, and as such has become a common gateway for viruses. That said, the file might still be in use by a background service which BitTorrent uses to monitor the file system. Worst case scenario you might be dealing with a virus or root kit. I would advise you run a virus scanner, or if you don't already have one installed, consider having your system serviced by a professional and let them know you suspect a virus.