I updated from 4.18.8 to 5.1.2 , not pro just the basic. After a download starts i leave it then when i come back to my Mac there's no connection anymore, whenever i try to quit it refuses, force quitting does nothing so i have to restart my computer every time. I repair disk permissions but doesn't fix the issue. I have trashed this newer version in favor of an older one that actually works.

Intel iMac
OS 10.5.6

LW 5 does not behave well for everyone. And does not like lots of incomplete files or lots of shares. So unfortunately will be slow or hang for some people. If you had any problem installing the old version, simply remove the 'install limewire.pkg' file from the receipts folder in Library. Receipts folder sample image. But sounds like you already knew what to do.