Generally, if it is your stock AI and not flyable aircraft modified to work as AI, I would think that the culprit was a corrupted or modified Halo.bmp, simply because that is the file that the navred, green, and white are drawn from. Try going into your main FS texture folder...look for the Halo.bmp. Then look and see if there is one next to it called something like 'halo.bak' or'halo.old'. If you find one, rename the halo.bmp to halo.new and the other to halo.bmp....then give it a try. OR...I could be entirely wrong and this may not help you at all. Let us know.