Supposedly the java files included with the newer quicktime are not backwards compatable with previous releases. I'm not positive if this is what caused your problem (as I've updated just fine on my mac), but it could be related. Is there a reason you haven't updated to the latest Java? It should be listed in Software Update as a Java upgrade. I recommend getting it, it'll greatly improve LimeWire's speed as well as allow you to use a few new features in the upcoming versions.