[zaphod]

Dude - post your config - it'll help us.

1. check the battery voltage with a multimeter - IIRC - it should be ~3v
2. swap out your sticks of ram - try running with only one stick which works for sure.
3. any error beeps on bootup ? - if you have the d-bracket with the LED's , whats the light config ?
4. remove the power switch connector from the mobo and try starting by shorting the terminals with a screwdriver - for all you know, it's just a loose connection in the power switch
5. are you overclocking anything - run the bios on fail safe defaults first

My money's on your mobo gone bad but you never know....

(I can feel your pain - ive been experiencing a run of problems over teh last one year - omne mobo dead (gigabyte km400vm rev 2.0) , 3 6800GT's PCI-E.....2 hdd's , and one mobo - MSI neo4 ultra showing the infamous battery drain problem now- I'm going to get the earthing done again and see if it helps - and put a big stabilizer on the mains)