My friend recently installed Sauerbraten on his computer, but when he runs the program, even on the loading screens, the screen "spazzes out", I will put up a video soon, but I have this for now:
C:\Program Files\Sauerbraten>bin\sauerbraten.exe -r
init: sdl
init: net
init: game
init: video: mode
init: video: misc
init: gl
Renderer: RADEON 9550 (ATI Technologies Inc.)
Driver: 2.0.6288 Release
Rendering using the OpenGL fixed-function path.
init: console
init: gl: effects
init: world
init: sound
init: cfg
init: mainloop
-slash
Incompatible video drivers. The end.
slash, that output seems pretty normal, like any other sauer.
Here's what i would try to do, sauer probably made a config, change all the video settings manually to the lowers possible, try even windowed mode. That might help.