What version of Java are you using (in LW click on Help > About LW & you'll see)?

Try this Java version. Use the JRE offline installer & remove your current Java version (Add/Remove programs) before you install the new one.
Archive: Download Java 2 Platform Standard Edition (J2SE) 5.0 Update 11

If that doesn't help, try the other fixes in this thread.
Fixes for LimeWire