When you got rid of the NAT firewalled error on Azureus, did you use UPnP or Portforwarding. Limewire should be exactly like Azureus to Portforward. The only difference being the listening port setup (In Azureus you only choose 1 port, in Limewire 2, but they should be the same port). Also if you use both at the same time, then you need to use a different port for Limewire, than you use for Azureus.

But it really sounds like the files you are having trouble with are just bogus files. A rule of thumb can be if you get more than 1000 results for a search, and you haven't used get more results on it, then most likely most (if not all) are spammed bogus results.

Lots of tips on how to avoid them here (does not just apply to music):

http://www.gnutellaforums.com/showthread.php?t=56904