Well, to start off, I know this has been an issue in the past. Apple released a patch for Leopard and Tiger, I know... The patch itself is built into Mac OS 10.5.1, so I shouldn't need to install it. Anyway, the title speaks for itself, my iMac seems to freeze during full screen applications. I get a complete lock up, nothing responds, no mouse, no spinning beach ball- nothing. Here are my specs: 20" Aluminum iMac, Intel Core 2 Duo clocked at 2.66 GHZ 6MB L2 cache, 4 GB DDR2 Ram, ATI Radeon [mobility] HD 2600 Pro with 256MB vram, 320 GB HDD (early 2008 iMac) Running Mac OS 10.5.6 and Windows XP SP3. The freezing instances in OS X only happened while running VM Ware fusion. The first time it was not full screen while installing Windows 7, but happened when the screen saver was on. The second time in OS X was running VM Ware full screen in Windows 7, doing the performance test. In Windows XP (via bootcamp) it happened while playing Half Life 2. The first time I had paused the game, got up and walked away for about a half hour. When I came back it was completely frozen. The second time was playing Half Life 2 again, and I was running toward a chopper firing at me and the audio clip started to skip over and over while everything else froze and it never came out of it. I think there was a third time, but I can't remember for sure. All hard restarts were necessary to get out of it. After the chopper incident mentioned above, I rebooted into OS X and used smc fan control to boost the fans a bit. I then rebooted and played more Half Life 2 with no crash issue. Any suggestions or ideas? Sorry if this was already posted... It seems to me that it may be a heat/ the iMac having trouble controlling the fans... Anyway, any suggestions would be much appreciated. Thanks.