Is this the first version of LW that you've had on the Vista computer?
Just try deleting LW's preferences folder - it might not help but then it might
Check here for instructions:
LimeWire Pref Folder in Vista
The main thing to remember is that LW has to be completely closed before you delete the folder - otherwise it won't have any effect.
If you haven't tried LW 4 with Vista, install 4.18.8 & see whether you still have the same problem. You can download 4.18.8 from your Pro download page - there's a link on the left hand side 'get LW Pro classic'.