Have a customer with 4.99 software and has 16DLI cards in slots 1,2,3. At least once a week some IDCS 28B phones stop working (blank screen).
Customer performs a card restart in 806 and phones come back up for a few days. Haven't nailed it down to one particular card. Thanks.

Cooling fans running? Processor does shutdown 24hrs or so after the fan stops running.
You could have a failing PSU as well.