Did you delete LW's preferences folder & disable performance options, as well as updating Java?

If download progress goes backwards then it can mean that there's a corruption in the file.
http://www.gnutellaforums.com/downlo...wards-why.html

Are you checking files with Bitzi before download?
How to use Bitzi

Have you tried downloading different versions of the file(s) to see whether that makes any difference?

If you hate LW 5 then see the link in my reply to your post in April - there's info about how to revert to LW 4