There currently are two reported, but as-yet unresolved stability problems with the FreeBSD/amd64 BETA graphics driver:
- Upon shutting down X, the system may crash with a kernel panic outside of NVIDIA graphics driver code; it's unclear if this is due to memory corruption, a driver/kernel interaction or a kernel bug.
- When powerd is enabled, the system may hang some time after starting X.
I doubt that high memory usage is a problem in your case. I'd be curious what the panics look like on your system. If you could capture them with DDB, that would be very useful. Please also generate/attach an nvidia-bug-report.log