I think it's pretty common actually. The first time it happened to me, I brought it up on the maya chat and it has happened to almost every else as well. Just close and re-launch maya again and it should be fine. I just did the softquadro patch to my msi TI4200 128 this morning so now I'm running a virtual Quadro 700 XGL. Will be curious to see if the above artifacts still show up occasionally or not.