The most common problem is a corrupted file during the upload, but it could be anything.
check the log history. that will give you a better idea whats going on and how to fix the problem.
if your still stuck, send the log to George - GLuft3 , he is good a decode the logs.
post your problem on the archive message board and or to archive.org. sometimes they can fix a problem on their end. they are slow and it can take weeks to resolve. (i don\'t complain, because it\'s basically a free service)
gook luck,
also,
when uploading, don\'t use your computer/Internet. this will increase your chances of a error free upload. I do my uploads overnight while sleeping.