Half downloaded files won't continue but new ones from the same source will

[Whare Whare]

Hello. I was downloading a few files from 10 files on a torrent last night, and all of a sudden 0KB/s were downloading. I just assumed it was my bad net and slept. Today I woke up to find out that if I start downloading the rest of the files, it works. If I choose one of the old files and one new file, it only downloads the new file. if I uncheck the new file the KB/s will slowly drop to nothing. So something is obviously making u torrent web reject the files and I don't suppose it's that it doens't recognize the parent site anymore... What should I do? I downloaded quite a lot for the data I have, I'd really appreciate some help.