Just thought I would post my solution, till I get a chance to try Darth333's suggestion, im starting a new game and can not check it now.
Go in the options menu select Graphics, then Advanced change the detail from high to medium, then back to high and click ok.
Return to the game and you should be fine.
There are 3 or so maps this needs to be done, I wont list then since its obvious when this happens
Edit: PS, im using Omega based on 5.1.