When it first started happening I would sometimes get a BSoD.
This indicates hardware/driver problems.
First thing to do is make sure heat isn't the issue. GoPro and DSLR video is CPU-intensive to decode, and if you're re-encoding to H.264 that adds to the CPU usage. If you're using Hardware MPE and the GPU is being stressed, that's a potential source of trouble. Make sure all fans are operating and no dust exists inside the case. Then try troubleshooting your RAM. Pull out 2 chips and try rendering again. If it fails, swap the RAM chips.
Jeff