For some reason one version of Java works better for some than others ... you coud try jumping back to 1.4.2: http://java.sun.com/j2se/1.4.2/download.html (Choose the JRE) but not sure if that's the answer for you. Sounds like you need the latest!

Try deleting your LW Preferences folder whilst LW is closed; instructions here: Fixes for Limewire

When you open LW, Control, Alt & Delete keys & go to Process Manager & see how many times Limewire is listed.

How much ram do you have?
How much spare HDD do you have?
What type & model graphic card?