Lemerise, i just wanted to say thanks for your information. I have a MacBook here, same model etc. And for some reason it was not booting up at all. I did as you said, and used the screwdriver to get the machine going. One by one i added/connected the devices i had disconnected and continued to use the screwdriver to boot the machine. Eventually i tried to boot it with the keyboard/top connector plugged in. It would not boot.
After closer inspection of the keyboard, i saw that the little ribbon cable which has about .5cm of it's ribbon exposed in the battery bay was torn. Likely when the hard drive was replaced. Apple sucks for having that there in an area that is supposed to be user servicable. Anyhow, one of the connectors in the 16 or so wire ribbon was severed and another was about 1/2 severed. Had to use a magnifying glass to see this. At first i thought this machine would need a new logic board, but now i know that it works fine, and it just needs a new keyboard. I am going to take apart the keyboard to see if i might be able to replace this ribbon somehow, as the keyboard is perfect, aside from the minorly torn cable.
Again i hate apple for making this design, but thanks for your information.
Unfortunately i was unable to take apart the keyboard. But however, a friend had some rear-defrost liquid connector material on hand (for linking the metal contacts in the rear window defrost of vehicles). I thought, since the keyboard is a write off that i would try to apply some of this liquid to the broken connector. It took a magnifying glass, someone to hold a pen-light to the connection while i worked, and a steady hand, but i managed to wipe it onto the broken connector and re-create the circuit. When it dried i connected the keyboard connector onto the logic board, and it booted the machine from the keyboard. Also, all keys work fine.
I consider this just a temporary fix, but it could be a permanent one.. its only been working for about 30 minutes, and i'll likely forget about this post by the time i realize its a permanent one..
Will be covering that exposed connector with electrical tape when i pput it back together, so this doesnt happen again..