Which OS do you have?

If you are using any of the OS'es under X, have loads of *real* RAM and using the LATEST VERSION OF LIMEWIRE (v4.0.5) increase LW preferred memory 200%-300%.

Rebuild your desktop w/extensions off using Techtool Lite.

http://docs.info.apple.com/article.html?artnum=18278 Mac OS: Assigning More Memory to an Application Program. The same directions are also in the OS Mac Help Menu.