I sorted out a similar problem for a pal who had updated PowerDVD3 to version 5; he had a Creative Banshee graphics card and I eventually, after much ferreting, found out that it needed a very specific updated driver.
He wasn't using TV Out either, only the monitor to view manufacturers' stock lists for his retail outlet.
However, finding a source for this driver proved a nightmare for some strange reason - in the end, I found a download source on a Mexican university's website, the driver having been recognised only by its file name.
Fortunately it cured the problem and the error message finally disappeared.
So an updated graphics card driver might well cure your problem, especially as Windows98SE is involved in both cases.