Clean installation of Win98SE, driver/powerdesk from Win98SE CD,
run of DxDiag (from Win98 installation in Program Files\directx\setup\DxDiag), test DirectDraw works OK, test Direct3D, works with software mode, hardware mode gives a white window with nothing more happening, mouse is responsive but that is it, machine has to be powered off.
Remove driver with Matrox special uninstall utility. Install latest 08/31/98. Same behavior.

And sure enough D3D game are locking the machine up.

Known issue ???

Thanks.