It sounds to me like you don't have all the OSX 10.4 updates. I think java 1.5 now is the default for all programs to use. Otherwise, force LW to use java 1.5 using the following technique & I think your LW will behave a lot better. Setting up Java 1.5

It might also be a good idea to delete the LW preferences folder whilst LW is CLOSED. You can find it here:
/Users/your_username/Library/Preferences/LimeWire

* Other ways to reduce LW's drag on your system:
Go to LW's prefs>Speed & tick disable Ultrapeer Cap. & press apply button.
Set both uplds & downlds to autoclear.
Close all LW windows you don't need open at that time. eg: Connections window.
If you're not in front of your comp, then hide LW in the dock.
Reduce uplds to about 70-80% or more. Reduce downlds to 80 or 90%.