key not recognised in windows

I have been using a Mac keyboard on my win 7 desktop for about 6 months as I love typing on my MBP waaaay more than other keyboards. Anyway about a month ago the f1 and f2 buttons just flat out stopped being recognised. I mean they don't even register if I use a keyboard diagnostic tool and strike the keys. Every other key works fine. Here is where it gets odd. If I press a key (any key) and then press f1 or f2, they suddenly register as being pressed...so they do work, just only just as long as I'm holding another key down at the same time. I have a plugged it into an older xp machine and it works fine straight away, I have plugged it into a macbook pro and it works perfect too, so it is not the keyboard itself. I have an older G4 apple keyboard from times gone past in a drawer that works fine if I plug it into the win 7 machine so it is not general key mapping on the win 7 machine. The only problem is when I put this specific keyboard with this specific machine. I have done every combination of plugging / unplugging, uninstalling / installing drivers, starting and restarting in normal and safe mode to no avail. I'm thinking that the problem may be deeper in windows than I'm comfortable playing without guidance, possibly a software conflict somewhere.

I did play with some services in admin tools a few weeks back due to 15 min boot times on this machine and it may have started then (I'm not sure...how often do you press f1 / f2?). Either way it is a useless shortcut if I need to press 2 buttons to get it to work.

I'm desperate for help....

Thanks all,

Jason