This is seriously making me very angry. I'm running Mac OS X Lion (10.7.1) on my 2006 Mac Pro and if I try to play videos, my Mac Pro will lock up with a spinning beach ball and even if I force quit iTunes (or QuickTime Player), other apps start freezing too. It gets so bad that I have to completely restart the computer. So basically I'm unable to play videos within Lion (works fine in 10.6). Apparently 2011 iMacs suffered from a similar video bug (before 10.7.1) where their computer would freeze after waking it from sleep and THEN playing a video, but I have my computer set to never sleep and it doesn't matter if I have a fresh boot, a fresh install of Lion, it still freezes if I try to play more than one QuickTime video. My exact configuration is: Mac Pro, 5GB of RAM, ATI Radeon 4870 HD, 4 Hard Drives (Lion, Snow Leopard, Time Machine, Windows 7). Here are the things I've tried so far: 1. I put in my old Nvidia 8800GT video card... same exact problem. 2. Bought a new hard drive and installed Lion fresh on it (left everything at default settings)... same problem. 3. Repaired permissions 4. Reset PRAM So I'm thinking that it must be some sort of hardware thing... but why would it only do it on Lion and not Snow Leopard? Also, why wouldn't 10.7.1 fix it for me while it fixed other freezing issues for the 2011 iMac? I'm getting seriously really annoyed now. So my question is... does anyone have a similar configuration as me and has Lion installed? Can you see if your computer is affected as well? Note: Oddly, I've never had any issues playing Flash movies in Safari (which it seems like 10.7.1 notes about the freeze fix). Please post any tips you may have... I'm about to give up.