By default Windows is set to restart on BSODs as soon as it completes creating the crashdump. If for whatever reason KeBugCheckEx initializes the dump generation procedure but holds up during I/O due to some sort of failure, it will cause the BSOD to hang permanently until restarted.
I'd like to check a couple more things. Please provide us temps/voltages using HWInfo
with Sensors only
option checked. Log two 30-minute instances: one for idle, and one for high load. If you can get your system to crash during a logging session, even better. It'll retain what was logged prior to the crash. Understand that this is rather dependent on your chipset drivers and stuff. Make sure all drivers for your motherboard are up to date as well as updating the BIOS. If you have any software that came with your motherboard installed, please uninstall all of them. They can conflict with HWInfo sensor readings and they often harbor nasty bugs.