Toshiba Satellite M45 exhibits strange power/POST behavior.

Got this one handed to me in a dormant state - laptop hadn't been powered up in a while. Charged the battery for 15 minutes, and proceeded to restore the hard drive to its factory state using the recovery DVD (for the first time - I had to break the case seal to use it).

During the first powerup for Windows, the laptop locks up when prompting for a user name. Subsequent attempts to power down and up resulted in freezing at the Toshiba splash screen. There was one 512MB memory chip and I changed its memory slot and changed the chip entirely. There was no change in behavior.

I cleaned the heatsink, reseated the CPU, and replaced the hardened grease with Arctic Silver 5. I removed the mPCI WiFi card. I removed the battery and used AC power.

MHDD 4.6 essentially tested the hard drive to be good. There weren't any sectors that were bad, but there was a pattern of slower sectors towards the end of the drive. I also reseated the hard drive.

I flashed the BIOS from 1.70 to 2.00

I'm still getting lockups ... BUT ...

... they go away when I slap the laptop on the keyboard area. I have yet to slap the underside, but I'll probably start doing that instead ...

... unless I can figure out whether there's a link between what I'm seeing and a possible issue with a bad ground on the motherboard.

Any thoughts?

Thanks for reading!