Comment 6 for bug 774089

My Macbook Pro did the same thing too.

I want to add that it was also getting hot. The CPU was obviously working hard, I guess.
The Applestore employes replaced my motherboard (on warranty)

I have a mid 2009 13'' Macbook Pro:

  Model Identifier: MacBookPro5,5
  Processor Name: Intel Core 2 Duo
  Processor Speed: 2.26 GHz
  Number Of Processors: 1
  Total Number Of Cores: 2
  L2 Cache: 3 MB
  Memory: 6 GB
  Bus Speed: 1.07 GHz
  Boot ROM Version: MBP55.00AC.B03
  SMC Version (system): 1.47f2