MacMini crashing after changing memory? After I bought a new MacBook Pro 2011 with 4 GB or RAM at 1333 MHz I decided to switch the RAM with the one from the old MacMini 8 Gb at 1066 MHz.

Initially I was expecting to have problems with the MacBook Pro, but it seem to have no problems running with 8GB of RAM at 1066 MHz.

Still, the surprise came form MacMini which became unstable and unusable (crashes or stops randomly but very often). I am wondering if the RAM is the issue or something else, like cooling.

How can I easily detect the source of the problems with the macMini? I mention that the 1333 Mhz worked just fine in the MacBook Pro and I know that it should have no problem using it, theoretically.
The Mac mini (mid 2010) is extremely finicky accepting RAM with a faster clock-speed (some work, some don't). You must use 1066 MHz or buy a pair that is known to be free of issue. For some reason that particular model was extremely sensitive to any discrepancy in RAM (many posts on the internet regarding its inability to run under these conditions).

For what it's worth, the new Mac mini (mid 2011) do not suffer from the same problem, accepting higher clocked RAM without complaint.