Funny glitches like that tend to be graphics related.

He may be best looking on autodesks qulification chart as even though cards on a Mac are "qualified" (Gforces etc) they still suffer glitches that are similar to the same card on a PC, they generally say what the problems are and this may be one.

He might also be best looking on other forums to with the card and the version of maya he has to see if there are any solutions.