Post the 10.8.3 upgrade, experiencing system lockups on startup. If I'm able to make it past the login screen, anything graphic intensive will freeze the system. First noticed with using Youtube. Crashes using either Chrome, Safari or Firefox. Restarting into Safe mode (the only way I'm able to post this message) seems to bring back the system. Console shows odd logs about starting a GPU diagnostic and just line after line of kernel messages. Have completely pulled all the hardware out of the box, cleaned and blown out memory boards, video card, drives Have run the Apple Hardware test with no errors Have run Rember to test the memory, no errors Xscan shows no errors, no temperature issues SSD is running the latest firmware. Running the last available SMC Version Reset NVRAM Tried restoring from Time Machine onto a completely different drive to rule out the SSD, freezing still occurs. Tried rolling back from Time Machine to 10.8.2 but still crashing My first though its the video card. Could possibly be time for an upgrade. 5870 or 6870 perhaps If its not video related, what else could it be? Open to suggestions. Thanks!