Any log message would be welcome: is there an error reported? Can you ssh to the machine after crash? Can you provide the log report as stated n »»»»»»»»»» If you have a problem, PLEASE read this first «««««««««« - #2 by aplattner?
If there is no error whatsoever, it could also be a PSU issu, or a card defect. Have you tried to RMA it?