Proliant 1600R halted

[CA1270591]

Hi,
we've run into a strange problem. It happened lately that our Proliant 1600R halted because of some reason. After rebooting,not even BIOS or graphics initializates. All parts are powered okay, but the screen doesn't init and not even an audible signal is given.

Powering it off for a few minutes doesn't help. However, if we wait for a longer period (few hours), it will start-up again normally (or sometimes a notice 172 - System configuration Nonvolatile Memory invalid appears).

I have tried to disconnect all the unnecessary periphals (left there just CPU & mem), but that had no real influence. Still have to wait to get it working again. All fans are working ok and the CPU doesn't appear to be overheated.

Appreciate your help ASAP