Power Button only works at startup, but non-functional afterwards

For a Macbook Pro 15 "
A1226 / OS 10.6.8 / 2.2GHz Intel Core 2 Duo

(1) When the computer is on, and i press the power button , the shutdown menu used to come on, but does not now.

(2) When i press & hold the power button, the computer does not force shutdown, even when i hold it down for 30 seconds.

(3) When I shutdown the computer via the apple menu, i cannot start the computer up using the power button

(4) However, disconnecting the trackpad ribbon cable from the logic board, then reconnecting, the power button is operational allowing the computer to start back up

(5)When I put the computer to sleep via the apple menu, it goes to sleep, and i can wake it up

(6) When I restart via the apple menu, it powers down then restarts without any problems

(7)The force quit keyboard short cut will not work most likely in that it uses the power button as a shortcut.

So pursuant, to (4) above, it seems that the power button is non-functional after starting it up, and will only work after connecting/reconnecting the ribbon cable