Function buttons not responding.....HELP!

I turned on my MPC today, and for some reason all off the F buttons under the screen are not responding. They click, but nothing happens.
i opened up my mpc, but couldn't see anything wrong with it.

I wanted to laod a new OS to try fixing it, but i need to press one of those buttons to do it .

This is giving me a mighty big headache, so any tips would be very welcome.

you don't need the bottons to try a fresh O.S. Just put a fresh copy on a disk, put it in the drive and turn it on.

I loaded a new OS by holding the rec and overdub buttons on startup, but it didn't change anything.
I'm just going to give up and leave it for a week. Maybe it will fix itself somehow, 2000xl's have a strange selfhealing mechanism sometimes:lol:

If anybody knows if the F buttons are connected to the mainboard somewhere, please let me know, maybe a connection has coome loose. I checked but couldn't find it.
I'm ussually pretty good at fixing electrical stuff, but i'm afraid to damage my mpc by completely disassembling it.
The buttons are OK. They click, and if i short the connection on the back of the printboard nothing happens either, so the problem is somwhere further up.