This will seem like a stupid question, but are you sure your resolution is: 1024/768?
I'm assuming you want to play on fullscreen?

1) You don't have vid_restart in your cfg.
=> next map gets loaded, than some settings will change after a vid_restart.
this is not 100% correct, but loading a new map, while you /exec'ed your cfg in the map before, can work as a vid_restart.
=> your screen gets fucked up.
(for example the gammabug works like that).

My best guess is that the resolution 1024/768 isn't the right one for your screen.
Try something else, an other resolution in your cfg.
Then do vid_restart.