I have had a few random non-reproduceable crashes in L5, not all the time, just often enough to be annoying. While trying to track down some non-L5 stability problems with my mac, I tried a couple of things and have noticed that I haven't had an L5 crash since:
I completely removed SIMBL, SIMBL Enabler for Sandbox, and SIMBL plugins (Afloat, Menu & Dockless), and completely removed Intego Virus Barrier.
It could just be a coincidence, but if you're having random problems and happen to have any of those installed (or any other SIMBL plugins), its worth a shot.