fx 5200 DVI output not working at higher resolutions

DVI won't work at any resolution above 1280x1024

New HP LP2065 flat panel monitor 1600x1200.

Graphics card Sparkle FX 5200 (SP 8834 - DT) 128Mb AGP

PC Athlon XP1700 - Win XP SP2 - 1Gb ram - AGP 4x slot on mobo

Nvidia drivers reinstalled v. 91.47

All resolutions including max 1600x1200 work if I use the analogue (VGA) output on the graphics card. Obviously I'd rather use DVI-D but if I try it at a resolution of 1600x1200 I get a black screen with a white bar down one side. The monitor's own menu said the input was 202x1200 resolution 74.9Khz 60Hz. I did briefly see it work for about a minute when I used the nvidia popup menu to change the res from 1280x1024 upto 1600x1200.

The fact that it works via analogue suggests there isn't an inherent system limitation. I'm guessing it maybe a timing issue?

Anyone had similar problems.