If you upgraded to Pro from LW Basic, it's often recommended to delete the LW preferences. See point #3 here:
Fixes for Limewire (click on blue link). LW needs to be closed at that time. See if that helps at all.
If still problems but the program is able to at least open, go to LW's menu bar, Tools -> Options -> Advanced -> SuperReallyAdvanced -> Performance, and disable Ultrapeer, DHT, and TLS.
If there are any java updates, install them.
Make sure you still have a copy of your Pro installer just in case.
I presume you are using Windows?