I've got a 22.214.171.124 kernel to 'work' at the moment. It sometimes takes several hours before a crash happens though. And I also need a realtime-preemption patch, but they are available for 2.6.17 but not 2.6.17.x. Using realtime-preempt with 2.6.17 is what I had originally, where the 'nvidia' driver worked but the rest of the system was not stable.
Thanks for showing me this, I didn't think to check for a realtime patch to the nvidia driver itself. I'm now using this patch; this might stop the infrequent xruns in jackd that I used to suffer from, but until I get a realtime kernel working I won't know.