As above, whatever is displayed on the screens continues to be displayed. But everything else is completely unresponsive. Only a hard reset or power cycle gets the computer out of the crash.
On restart, it boots just fine. Again without any error messages. It doesn't even display a "you didn't shutdown your computer correctly" message.
Are there any hidden log files, a monitoring program etc that I could enable or check? As at this stage I don't even know if I have a software fault or a hardware fault.