Same problem with many laptops. D610 design flaw?

Over the last 3 months I've had a rash of serious and identical faults on a half dozen of my Latitude D610.

The will all shut down completely and without warning. Dropping to power off mode as if you'd yanked the power and battery out of them.

There are no bios error messages (Version A03) and no error log (bios version doesn't have one). Dell's diagnostics reports that everything is OK.

It's not the battery, mains lead or memory as I've changed them all and still get the problem, and it's not software as it happens when using known good Windows installs and when booting from a Unix based boot disc. After the first shutdown, outages become increasingly frequent until left for a period.

The problem appears to be heat related (all standard heat precautions already taken) and I had one A06 bios report of a heat failure on a laptop experiencing exactly the same problems.

The laptops are getting overly hot just under the CPU and around the buttons at the top (above the heatsink), the fans are working. All of the effected laptops were supplied at the same time.

Anybody have any ideas or any similar problems.