While I was investigating my problem of a stuck shift key I found multiple answers that pointed in a faulty mainboard direction (I had a moisture spillage on the laptop).
After the spillage had happned I disassembled the complete laptop, put the top cover with glued-on keyboard complete in a very hot water tub and let it stay there for a while, to clean out the moisture residue, also the trackpad which didn't register hardware cilcks anymore. I managed to compeltely clean out the microswitch under the trackpad, it clicks really snappy again but it still doesn't work, neither was the problem of the stuck shift key solved. You can switch "Touch pad to click" on in settings and that works once booted.
Currently I'm using the macbook pressing C or Esc key while booting (both work in snow leopard) and I use a small wireless iMac keyboard with it as external keyboard. I already tried installing OSX Lion on this macbook but had to revert to leopard, no audio/webcam and unable to do a normal system boot. I thought I had a corrupt lion install but swapping the lion harddrive to my mac mini worked ok. I must admit i didnt know about pressing C during boot maybe that still works under osx lion.
Regards Jeroen.