After ensuring its not a software issue (virus, spyware, drivers, updates) by doing a clean boot and waiting for the crash,
I would start with a visual inspection of the motherboard and video card for dodgy capacitors.
If they all look ok then the PSU could cause this.
Intermittant faults are a pain. About all you can do is replace part by part until they stop.
Event logs might help, but just as often I have seen video cards produce event log errors due to a faulty PSU so use them as a guide. The error you are getting is a prime example of this, its generated by the motherboard, but this dosent mean the motherboard is faulty.
Knowing what brand all the equipment is will help everyone point to known likely issues too.