My asus vw202 widescreen 20"

Question

my asus vw202 widescreen 20" monitor refuses to go any higher than a resolution of 1024 x 768. It's supposed to go up to 1680 x 1050. My graphics card is an nvidia 7300gs which should definitely go beyond 1024 x 768 - I have friends running higher than this on lower power graphics. I'm using the Asus monitor driver downloaded from their site. I have had the monitor higher, briefly - then it suddenly shrinks the display to half the screen - and refuses to go beyond 1025 x 768. I've returned the monitor once to PC world - where it appeared to work - however maybe this is anintermittent fault. Any ideas ?