If you've changed skins, try changing them back. Sometimes changing skins will have side effects.
It may be a conflict with your graphics card setting or driver. See
http://www.gnutellaforums.com/showthread.php?t=39600
Or try deleting your .limewire preferences folder. Points 2. and 3. while limewire is closed:
Fixes for Limewire when LW isn't operating as it should!
Also make sure your Java's up to date. Use the JRE offline installer here & remove your current Java version before you install the new one.
http://java.sun.com/javase/downloads/index_jdk5.jsp