had same prob on old puter
delete the video.cfg file in ah folder
when setting video on startup-go to lowest option(cant remember what it is-not on home puter now) -also set frame rates to minimum -whatever it is--as above

Make sure ground clutter is off--Cntrl C ?
Go to lower resolution --Shift F2 or F3
See if that alleviates some of problem - and then change from there
NwBie