Since the PC is off, it's unlikely and driver on the PC is going to affect this.
A discussion in another newsgroup found their display had suffered a mild, but totally fatal failure. Try it back on the 98 PC to see if it died.
I've been using a GemStar VESA/DPMS-compliant LCD monitor for a couple of years with a Win98 computer. Now, with a new eMachine XP system, the monitor will not turn off (hibernate) when the PC shuts down. Also, the panel buttons on the monitor (size, brightness, etc.) won't respond when it's connected to this system. Is this a driver problem with the computer? What can I test to pin this down? Thanks!