Since we updated to Snow Leopoard and Final Cut Studio 7.0.2 / 7.0.3
we have some strange things going on with compressor. Sometimes when we want to compress a clip with a cluster (quickcluster with services).
We get the BSOD of apple... The black screen of death that tell you to force shutdown the computer...
We have a lot of computers here and this is not happening to only one.
That often means a hardware issue.
Although the first thing I'd consider, if you updated FCS before updating to Snow Leopard they you should try reinstalling FCS. BTW once you install an OS you should update it using Apple's OS Combo Updaters and not Software Update. The latter unfortunately doesn't always do a clean job of replacing OS components.
Do you have any third party hardware devices hooked up?