Viewsonic monitor - no display when reboot WinXP

I have a Viewsonic 2025WM LCD monitor that works extremely well but
has an annoying problem.

If I reboot Windows the display flashes at 1second intervals, it
alternates between a blank screen and the DOS boot up messages, it
then stays completely back as Windows loads. The power Led on the
on/off button then flashes.

If I unplug the monitor from the mains wait a few seconds then plug it
back in I have a display again.

Anyone come across this before?

I have the resolution set to the recommended 1680x1050 60Hz 32bit
colour and a ATI Radeon 9600 AGP video card.

tnx

John