This could memory or video problem, I recommend checking with different memory since your processor supports DDR3-1066/1333; also make sure you are using the latest graphics driver available at
Thanks for the tip,
Apparently the rest of the hardware supports the ram clock, and when using external video card it is not a problem for the ram to be at 1600 MHZ, but using the built-in card requires a ram frequency of 1333 MHZ.
I've set that 3 days ago and so far there are no crashes or problems of any kind.
Thanks Allan for the fast and correct response!