Still an issue with latest 270.18 beta driver.
$ dmesg|grep NVRM
[ 5.265666] NVRM: loading NVIDIA UNIX x86_64 Kernel Module 270.18 Tue Jan 18 21:46:26 PST 2011
[ 18.470535] NVRM: os_raise_smp_barrier(), invalid context!
[ 18.485152] NVRM: os_raise_smp_barrier(), invalid context!
[ 101.598273] NVRM: os_schedule: Attempted to yield the CPU while in atomic or interrupt context
It's as unstable as ever, no improvements over earlier releases. And now the "os_raise_smp_barrier(), invalid context!" messages are back as well. Those were not present with 260.19.29 (at least I did not observe them even once during testing, but have seen them in earlier releases).
Again, I urge you to please look into this, or at least provide some form of feedback (e.g. if this is not a nvidia problem and Dell has fscked up their hardware or something in the Linux kernel is b0rked and there's nothing you can do.).
Attaching updated bug report log using driver 270.18.