Maximus Formula Startup issue

hi there

Recently my system have been acting strangely, I was away for 6 months and on return I found that when I started the machine it hung on the POST screen, right before detecting the drives. It works fine when i pressed the reset button. So I thought it might be a duff battery on the MB and replace it with a new one. Still no change so I thought maybe the battery I replaced it with was faulty as well... nope no change... what do you think can be the issue?

System:
Asus Maximus Formula
5Gb RAM
2x 1TB HDD
1x500Gb HDD
MB Supplied Sound card riser
Gigabyte GeForce 8600 Silent display
Intel Q6600 Quad Core CPU
Phillips DVD-RW+
Phillips DVD

The system is not overclocked and just running normally

regards
R