Since owning the macbook pro I use it everyday for at least 8 hours, have it set to the 9400M, last month I created 5 60min dvd's using a panasonic hd camcorder, imovie and idvd so I had set the macbook pro to use the 9600M, it got hot but never noticed any issues.
I set the macbook pro back to the 9400M and it was fine until today, the macbook pro wasn't even hot when I had the issue.