Thanks ant, though I now have the problem sorted.
Basically it didn't like the way I originally had my display settings. At first I had my monitor 2 displayed to the left of monitor 1 (Monitor 1 being the main 22" CRT - and Monitor 2 was a 17" TFT sat to the left displaying my Graph Editor etc) To solve it I switched the display back to (1 2) not (2 1) but using nVidias options I set my main display to monitor 2 (ie 'Windows' is displayed on the right hand monitor - the big CRT)
Hope that makes sense...
btw One of the guys at work really liked the 17" TFT and asked if I wanted to swap - so now I have 2 huge 22" beasts on my desk! I think he's mad as I deffinately got the better bargain!