I would not expect vram to cause that selective of a problem. It looks like its affecting specific elements of the screen (rectangular areas) as drawn by quartz. (operating system problem)
I've seen VRAM failures affect specific elements of the display, because on modern Macs the drawing of display elements such as windows is handled by the graphics processor (a window in OS X is a 2D object with its contents surface mapped onto it, which is why you can do things like move windows even if the spinning pinwheel is up). If the place in VRAM where the texture map is stored is faulty, you can see weird things happen to certain elements rather than to the entire screen.
