Strange boot delay

Have W7 32 bits.
For no apparent reason it takes 30 secs or more for POST to appear on the screen.
Tried three ATI graphic cards, all the same issue.
W7 starts normally.
Maybe unrelated but sometimes I get a blue screen in W7 and the pc shuts off, restarts normally but does not load the ATI driver.
After a few reboots it does load again.
Did not change anything, mobo is Asus P5Q3 DeLuxe, tried three bios versions, no luck.
Can it be the mobo battery? Think not, because if flat nothing would happen right?

I posted in this subforum, because I am unsure if this is really ATI related...

Check all your mobo cables and connections. You may want to try swapping out the mobo.

Also try clearing the CMOS: Clear CMOS - 3 Ways to Clear the CMOS - Reset BIOS

Test your RAM for 5-6 passes with memtest86 CD.