Two things to try.......spray the socket where the ribbon cable inserts with an electronics cleaner.....sometimes it builds up corrosion and does not make a proper contact....you could insert the cable and move it in and out to help losen any built up corrosion....this might help......(do this carefully....you do not want to damage the ribbon cable by bending it).
The other.... you miight have what is known as a cold solder connection (basically the solder is broken in one of the points of the socket were the ribbon cable plugs in)...this could happen when you move it inserting the ribbon cable or press too hard and the clamp.......sometimes....i
http://www.ehow.com/v
I said sometimes because used solder contains some of the dissolved base metals and is unsuitable for reuse in making new joints. Once the solder's capacity for the base metal has been achieved it will no longer properly bond with the base metal, usually resulting in a brittle cold solder joint with a crystalline appearance.
It is good practice to remove solder from a joint prior to resolderingdesoldering braids or vacuum desoldering equipment (solder suckers) can be used. Nevertheless, hand-soldering techniques require a great deal of skill to use on the finest pitch chip packages. In particular ball grid array (BGA) devices are notoriously difficult if not impossible to rework by hand....
by: edbedbPosted on 2009-10-08 at 17:58:55ID: 25531674
You tried everything there is to try to repair the hardware, other than change the motherboard.
I ran across this the other day while troubleshooting a different problem. It didn't fix that, but it might work for this.
There is a value named PollStatusIterations. The way I understand it is that it sets how many times the keypress is checked before accepting the value. It is probably set to 1. I would try increasing the value. Only thing is, the higher the number, the slower the keypress response.
Open regedit browse to HKEY_LOCAL_MACHINE\SYSTEM\
Select ACPI then search for this value: PollStatusIterations. Press enter then change the value.
Then continue the search, there are probably more than 1.
It's a shot in the dark, but what do you have to lose.
Post back if you need help with this.
By the way, this can only work after Windows is started.