How maddening ... I concur with a fresh restart... that is, drop the components down to only the bare basics - as little as one dimm, no sound card etc, no OC panel... nothing that is not absolutely needed. Then reinstall OS or even just try fist without anything "extra" with the current installed instance of the OS and then try flattening and rebuilding it.
I don't know if any of the component testing tools test sound cards - that seems like a good candidate to start with in terms of removing.
Also, what does your system and/or application event log have to say about the crashes?