unresponsive at startup after fitting a new screen

Hi folks, thanks for taking the time to read about my problem(s) with this little beauty.

History:

My client hadn't powered down her macbook for over 6 months due to forgetting her password and her fear of never being able to access her files again! But she needed a new screen so the inevitable had to happen.

I powered down the mac, disconnected the battery, swapped the screens, reconnected the battery and fired it up. I got power, chime, drives and fans and a black screen. Did a bit of research here and discovered a few others with similar problems, so followed some advice herein and ended up replacing a fuse. Worked like a charm, the screen lit up and the apple logo glowed triumphantly on the cover. My enthusiasm was short lived though when it sat on the grey screen with the apple logo. I tried to boot into safe mode, recovery console, disk utility etc but there was no response.

My next course of action was to remove the hard drive and caddy it to another mac to check it for errors. It immediately gave the warning that the disk could not be repaired and I should save my files (which I did with haste). I ran it on disk utilities and was informed that the MAC partition needed to be deleted as it was corrupt; so I did this and formatted it, rechecked it and everything seemed fine. Again feeling triumphant I put the drive back in, fired the mac up expecting to be able to do a clean install but again no response from the keyboard. The capslock doesn't even come on. I have checked the ribbon cable for damage and to ensure it is correctly seated in its clip but can see no obvious problem. I have tried a USB keyboard, which is also unresponsive with the exception of the fn light illuminating shortly after I power up.

A black screen, a corrupt hard drive and a non responsive keyboard would indicate to me that there was, at some point, a power issue that may have blown more than one fuse. Now I could sit at my desk every night for the next month and attempt to discover which component(s) on the logic board may need replacing or I could just ask if anyone has experienced this combination of problems before or could guide me in the right direction as to where I should be looking.

Many thanks, Fox