That's very odd that it won't let you install Pro over Basic. I'd suggest you trash Basic (or archive it.) Then go to OSX folder, Library->Receipts & remove Install Limewire. Receipts folder sample image. Then try installing pro again.

BTW you should NOT normally remove items from the Receipts folder as the system requires them.

Oh & did you open Java Utility & put Java 1.5 at the top of the list so LW will use it? The Java utility is found in your Utilities folder.
To check LW is using it, go to menu bar after you open LW, then click on the limewire word at top left next to apple icon, & select About LW. This will tell you which version of Java LW is using.