I am having the exact same problem. I also have configured ports according to sonicwall support, I even disabled Intrusion Prevention completely and still doesn't stop my limewire downloads being corrupted.

Sonicwall claim it's nothing to do with their product but that's simply not true. When I connect directly to my adsl router and bypass the sonicwall firewall Limewire downloads are fine, it is only when it passes through the firewall.

Anyone any solution to this. Do I need to configure my adsl router to forward to the firewall or something, I'm lost, any help appreciated.