I have installed GF 6800GT in my PC which runs Windows 98. When I try to switch resolution normally - as in display settings - everything is fine. I can switch every available resolution and refresh rate. Problem starts when I try to switch from desktop to a dosboxed game (DOOM for example) - my monitor then goes black and in gives info: "no signal". When I press ALT-TAB, it switches back to desktop - so the signal is back again. Then I press ALT-TAB again and I can play doom normally. The video is ok, no artefacts or other bugs, everything is just fine. I tested it on lots of DirectX and Nvidia (official/unnoficial) driver combinations and it's the same everytime. I probably tried every option in Nvidia panel. Still nothing sorts it out.

It's weird that i have this problem only with DOS games. Windows apps resolution switching is always fine.

BTW. Does anyone know how to set resolution override in RivaTuner?

[UPDATE]
The problem occurs only on DVI output. On VGA everything is normal. But still I want to use DVI to take advantage of display scaling.

[UPDATE2]
Switching resolution problem does not occur on "Standard Graphics Adapter (PCI)" driver. It seems the problem lies in Nvidia Forceware drivers.

[UPDATE3]
Another strange problem emerged - Nvidia Forceware drivers dont see the AGP bus properly. Nvidia control panel reports the card working on PCI bus. DXDIAG also shows AGP as disabled - regardless the DirectX, Forceware and Intel INF driver versions. On "Standard Graphics Adapter (PCI)" AGP is enabled.