I have a 2011 iMac with the 512mb Vcard. The computer works and runs great. HOWEVER. I have one weird issue. Whenever I run a second display it will shut off about every 5 minutes for 10 seconds. The monitor does NOT search for signal, but picture goes black for about 10 seconds. Other than that its running great. Weird because the monitor is still interfacing with the computer since its not searching for an input. Just goes black. Any ideas? Software? Heat Issues? Thanks!