I see hard freezes...
I've been seeing hard freezes, but they don't sound too similar (well, other than the hard freeze part).
I'm runnign RH enterprise linux 3 and I find that if I cause an OpenGL app to core dump (send it a SIGSEGV), it hard-freezes the kernel. Unfortunately, I don't even get the pretty light show :-(
No clue abotu what is causing it although I know a lot about what _isn't_ a factor (not the SMP kernel, not the driver version, not NvAGP being enabled..).