Try deleting your LW preferences folder; instructions here:
Fixes for Limewire
SOmetimes Java 1.5 doesn't behave very well on some people's systems or likewise for the previous version. Yo could try the previous version of Java to see if that makes it more stable: 1.4.2:
http://java.sun.com/j2se/1.4.2/download.html (Choose the JRE)