Was the machine working okay before you cleaned it?
It's hard to offer any suggestions because it could be so many different things. As a hunch check the key area thoroughly, make sure the correct key is inserted and its fully and correctly engaged, see if you can bypass the key altogether. I'm not that experienced on Q950's (I've never had one of my own) but we did have one where I worked and I know from experience that key could be temperamental.
Other than that I'd strip the machine again and put it back together making sure all the connectors are clean and correctly seated. I know it's obvious but mistakes do happen - I recently finished reassembling a Powerbook G4, plugged it and pressed the power button and nothing happened. I turned it over and realised I'd forgotten to plug the battery back in.
It's hard to offer any suggestions because it could be so many different things. As a hunch check the key area thoroughly, make sure the correct key is inserted and its fully and correctly engaged, see if you can bypass the key altogether. I'm not that experienced on Q950's (I've never had one of my own) but we did have one where I worked and I know from experience that key could be temperamental.
Other than that I'd strip the machine again and put it back together making sure all the connectors are clean and correctly seated. I know it's obvious but mistakes do happen - I recently finished reassembling a Powerbook G4, plugged it and pressed the power button and nothing happened. I turned it over and realised I'd forgotten to plug the battery back in.