Black screen! / But machine boots up

[Steve06]

Dear all,
all of the sudden, after having removed one of the memory modules of my T61 and rebuilt together the palm rest and the 4 screws on the bottom carefully, the machine boots up quite as usual, as I can tell by the beeps, the HDD activity and the Vista welcome sound, but the screen remains all black. There is not even the Thinkpad Logo appearing!
The backlight, however, works, but there is just not screen content.

I tried it on and off my advanced dock, which is attached to an Eizo external display via DVI.

I assume that it might caused by some loose contact. It even worked once and then again it didn't after checking the RAM again.

I did not open the machine further as necessary to access the RAM slots, that is dismantled only the palm rest.

Any helpful comments are very appreciated.
Steve

[Harryc]

Remove the palm rest and reseat the RAM module. Try both RAM slots, try another RAM module. Plug in the Palm rest connector (do not screw in the Palm rest yet) Power up to test.

[Steve06]

Remove the palm rest and reseat the RAM module. Try both RAM slots, try another RAM module. Plug in the Palm rest connector (do not screw in the Palm rest yet) Power up to test.

Tried all combinations, each module alone, both modules (one in slot 0, the other in slot 1, and vice versa) - it changed nothing.
So I don't think the RAM is the reason.

[sktn77a]

It does sound like a loose connection. You might want to try taking the keyboard out also and check all connections that are visible.

[Steve06]

The described problem was due to a defective motherboard and/or nvidia chip. After replacing the system board, the problem disappeared.