ScreenMode Problem with SDL
 

I have played some games that uses SDL: Armagetron, Unreal DEMO.
succesfull and I'm also programming my own games with sdl.
I'm running Fedora Core 2.
first SDL worked OK.
but then one day when I played armagetron(I have trouble with that to, I have to start about 30 times before it works) and the resolution didn't change, the screen just got smaller or bigger, the hardware screenmode didn't change. I have a Geforce 4 MX with the latest NVidia drivers.
I was lucky the screenmode that is used is my standard(1024x768)

any Idea what has gone wrong and how to fix it
I think I tried to reinstall SDL from FC2 Cd's, but had no effect