Well it's not related to the "texture" for sure.
I had the same happen to me, but only once, in Wellspring, along the border of Mick's Garage in the entrance door frame.
I agree it's probably video memory, because as I said, it only happened once, then it just stopped. Must have to do with how the textures were loaded onto the map during the loading of the level and all its assets.
Anyway I'm sure we wouldn't get this stuff it we has a better card, I didn't even think mine would run the game smooth... it doesn't exactly meet the minimum requirements, and yet it plays the game just fine
