Root bus error crashes server?!?

Since I upgraded my server to OS X 10.5, often when users get ROOT bus errors or segfaults, it kills the whole server. SSH (and everything else but ping) stops working, and I can’t even log into the console to see what’s going on as it’s “pinwheeling” at the login screen. I have to actually hard-reset the server, which my users don’t much care for.

Has anyone heard of this? These are normal, unprivileged users; there’s no way they should be able to eat my server.

This never happened in OS 10.4, for what it’s worth…

EDIT: ROOT 5.20/00, OS X 10.5.4, processor pegged on 100% indefinitely…