Which version of LW are you using & which version of Java (open LW > Help > About LimeWire)?
Try reinstalling Java. Go to the link here
Java SE Downloads & download the JRE offline installer. Remove all other Java versions installed on your computer via Control Panel. Next, install the version that you've just downloaded. Restart your computer.
If that doesn't help, try an older Java version.
If you're using LW 4, try this version:
Archive: Download Java 2 Platform Standard Edition (J2SE) 5.0 Update 16
And if you're using LW 5 (needs to have Java 6), try this version:
Archive: Download Java Platform Standard Edition (Java SE) 6u5
Just remember to remove any other Java versions installed, before installing another version. And reboot after installing