Well I have the ATI Mobility Radeon HD 6370. And my computer is a laptop with Windows 7, 64 bit. With a Triple-Core Processor 2.00 GHz. I actually played Guild Wars on this computer and its a good computer, you can play minecraft, Assassin's Creed Brotherhood, Battlefield 3 all on the same computer and it'll still run good. But for some reason this graphic issue keeps happening.
I have a very similar problem to this. Except once I log in, it clears. The character models are also really blurry. It also does this to me in game.
The game mechanics (fighting, waypoints etc) still function perfectly well.
Also, underneath all these random coloured things in the way, the original textures remain, but are blurry