CQ57-489wm no video at bootup!

I have a Compaq Presario, CQ57-489wm, laptop that won't power up. No video out what so ever. No Bios Post, nothing, and that's on the laptop screen or the VGA out port!
I googled the problem and it seems to be common with this model Compaq, CQ57!
One suggestion was to do a hard reset, remove battery, pull AC plug and hold down power button for 30 +secs.
WOW, afterwards this laptop booted up fine, all of the associated lights lit. Asked for BIOS password and then on to Windows Login password and up and running access to everything, working as it should!
I rebooted 3 times with just battery, just AC power and then both!
Fourth time about 15 minutes later, and back to nothing! The hard reset(from above) would no longer work. I removed as many peripherals and swapped out ram modules into different slots and solo as well. NOTHING. Hmmmm.
I put a marble onto the power button and placed battery onto it and let it sit over night with the power button depressed (as in hard reset above) . . . VOILA next morning booted up fine, asked for passwords working OK!
JUST ONCE!
Later in the day I tried again and was jiggling the AC power plug as it was starting/booting and again it booted up fine, JUST ONCE!

Any suggestions? anyone familiar with this CQ57 series problem? Is it indeed the motherboard? If so why is it so intermittent, and why does the hard reset seem to work . . sometimes?

Thanks Any/Everyone!