I have the same problem... Any files that end up in the "incomplete" folder stay there never to resume. There is no way that I can see to force them (it's only under the download window that you have this option). Also, there is no way to move these files into the download window. If you ask me, there should be a "force resume" button attached to this folder. If anyone else knows what i'm talking about and has an answer, please post it.
thanks