Ok, first up, a big thanks to all who replied.
Not quite sure what happened here, although i think it was my fault (usually is, according to my wife!!!)
I did some buggering about with ATI settings and all was fine until i changed the res 'in game'.
I have just done the 'Restore to factory default' on the monitor menu and all is as it should be

So, thats me not buggering about with that again
Thanks again,
Sav.