Hi there,
Sorry to hear about your trouble -- that's a new one on me. To be honest, what it most sounds like is some sort of graphics card driver issue; you might make sure you're on the latest version of your graphics card drivers. 1280x800 isn't a standard monitor resolution that I've ever heard of, so that's a bit odd as well; that may have something to do with it. Perhaps this is a netbook?
Regardless, what you can do is try manually setting the resolution in a settings.dat file that I've attached here. If you download that to your RuntimeData folder, then you can open that in a text editor (normally we don't post settings.dat files because they include license keys, but this one is stripped of all settings but the ones relevant to you).
Anyway, if you open that file in a text editor, you'll see lines for FullscreenWidth and FullscreenHeight. I've set those to 1280x800 for this one, since that's your resolution, but if that still fails then you might try other, more common resolutions. 1024x768, 1024x600, 1280x1024, etc.
If none of that works, you can always set add a line that says
IsFullscreen:0
That will then make it so it opens in windowed mode, and you can see what your options are in the in-game settings window. It automatically includes a lot of the common resolutions, plus whatever Unity 3D, the engine that AI War runs on, detects. Normally Unity handles all of this pretty automatically, so this is the first time I've heard of an issue like this -- hence my first thought being graphics card drivers.
There's also always the chance of a bad download from Steam; that happens from time to time and can give odd results. So you might try having it verify the local file cache in steam for the game to make sure it didn't corrupt anything.
Hope that helps!