Ram upgrade problems

[feildarcher]

I have just replaced my hard dirve after it was damaged, all working great, so I decided to ugrade the ram to 2 x 1 gig from 2 x 512. I purchased two matching cards and installed them, fired up ok but froze after 1 to 2 mins, replaced old cards, all ok, swapped the bottom card for a 1 g card, all ok, swapped the top card, freezing again, the T40 will only work with a 512 under the keyboard and a 1g in the lower slot. I have tried all cards in all combinations.
Any ideas why my T40 will not run with a 1g card under the keyboard but ok with the 512.
The thinkpad has not had a sheltered life thanks to my teenage kids. I only tried to repair it as it is a good machine when working.

[ZaZ]

Have you tried running memtest on the memory?

[feildarcher]

Have you tried running memtest on the memory?

no as both new 1g cards give the same result and work fine in the bottom slot.

[feildarcher]

Hi,it seemed to be a keyboard problem. changed the keyboard now seems ok.