Screen went weird

I was in pre-sear..across North Wall when suddenly my mini-map went strange..with no border and a white slash across it. I hit M and my big map had the names but no waypoints marked on it and when I went out the gate the loading screen was streaked browns like someone had scraped paint downward, though any of the lettering was fine. I went to log out and it allowed me to, but I could not find the minimize and close window icons on the screen. I re-typed my password and selected the same character but when I went back into the game the problem was still there. I logged out again...same screen and I clicked in the general direction of the X and it worked. I then rebooted and am about to try going in again. I am sure it will be fine now that I have done a reboot...but I was wondering what might have caused this?