look, try this: just set everything back to the way you had it in the beginning, or just make a clean install.
The, go to your .ini file and under display options, set the refresh rate to 60, and if it doesn't work, try different ones, for example, 75
[Display Options]
FullScreen=1
Disable Movies=0
Disable Intro Movies=0
Sort Modules=1
Width=640
Height=480
BitsPerPixels=32
RefreshRate=60