OK, another odd one, a torrent finished downloading, but instead of moving the file to the 'Downloads' folder, uTorrent then renamed the file in the files section to the name of the downloads folder, so instead of being 'TV Show 2x19.mkv', the file composition of the torrent simply contained 'Downloads', as a folder. Because the file name of the show it had just finished downloading was not 'Downloads', but 'TV Show 2x19.mkv' it promptly broke and asked for a recheck. This proved to be impossible however, as it now only looked for folders and not files. Manually relocating the download to the fully downloaded file worked, and the file checked through OK, but when asked to start again in order to upload, the file changed name again to 'Downloads' and promptly broke again. Manually moving the file to the 'Downloads' folder and starting again from there instead seemed to do the trick, and the expected file stayed correct, so the problem probably lies once again in the file move on completion process.