It will behave like that if they are fakes, or else, it can't get a good / available connection by one of those hosting the file. Thing is even if the hosts are showed as having the file, they may have all upload slots filled. If it's a video file, I'd recommend doing a Bitzi Web Lookup to check that it is a valid file. If it's a video file & it's not listed there, then that gives greater chance it's a fake file.