Blank unit placeholders?!!!

In my Karth-camp everything was fine until Kyrene sallied during AI turn. I killed all and the settlement became mine and.... wham! half of my unit placeholders became blank. The only thing that is visible is the amount of soldiers in each unit and if you hold the mouse-pointer over the placeholder it will still tell you what unit it is meaning that I can continue playing. This phenomenon occurs all over my empire: in settlements, outside and about 50% is affected. When I move a "blank" unit into another/ or a stack all units turns blank. It´s almost like a virus... or is it a new EB-feat, stealth-mode? ;)

I've seen this before, usually in conjunction with the "puzzle graphic" mentioned in another thread. I'm not sure what causes it but it usually goes away when you either after a few turns or if you save, quit, and restart the game. It's possibly a memory issue.