Hopefully someone can give me some pointers how to locate the problem...

I ran Skyrim fine with my old rig, Athlon X2-245, 9500 GT etc. Of course with limited graphic setting, but almost always Skyrim worked 100%.

Now I have built a new computer and everything is working very well, except for Skyrim.

I formatted my SSD drive, installed a new copy of Windows 7 Home Premium 32bit and got all the Windows updates.

My machine as of now is:

*Intel i5 2500k (stock clock for now)
*ASRock Extreme 4 Z77 with the latest 2.70 BIOS
*ASUS Radeon HD 7870 CU II OC (latest drivers, only factory overclock for now)
*2x4 Gigs 1600 MHz Kingston HyperX DDR3 DRAM (set to 1333 MHz in just to be safe with the gen2 CPU)
*Kingston 128-Gig SSD

...now. I can start Skyrim fine, but it will ALWAYS crash within 2-3 minutes. I'm running on Ultra and it works beautifully - but it crashes every time.
It just jumps very quickly back to desktop without any warning, without any error message afterwards. The PC works fine after that as well. It's just Skyrim that's playing tricks on me.

I really hope someone can help me with this... Other games work fine, Skyrim does this to me now. I'm thinking maybe a DRAM timing issue or something other BIOS related?