Try deleting LW's preferences folder when LW's properly closed.
LimeWire Pref Folder in Vista
This will change all of your settings within options, you'll have to go back through afterwards & reset things. If you're not sure of your settings, go through LW's tools > options & write them all down, so that you can reset things later.

If that doesn't fix things & allow you to change ports, try changing Java versions (hardly anyone's had a problem with 1.6.0_03 but see if this older version's any different).
Archive: Download Java 2 Platform Standard Edition (J2SE) 5.0 Update 11
Download the JRE offline installer & remove any other Java versions installed on your computer, before installing this one