I just did a fresh install of OS X 10.4 (immediately updating it to 10.4.1) on a PowerMac DP2.5/2G/ATI Radeon 9800 XT. I have not installed any other software to this system as of yet. I have connected the system to the net but not registered with Apple. Problem: When I try to view any of the H.264 clips in Apple's QuickTime HD Gallery the viewing area stays completely white (the audio on the clip plays flawlessly). Interestingly, the H.264 version of Macworld 2005 Expo Keynote, available elsewhere, works fine. Also, other QuickTime files work ok. This does not appear the be Safari related. For example, a downloaded copy of the BBC Motion Gallery Reel, also from the aforementioned HD gallery, exhibits the same problem. I have found one or two reports about this problem elsewhere on the web, but no resolution. QuickTime 7 was the primary reason for me to upgrade to Tiger (I plan to purchase the Pro key), so this sucks. Any ideas what might be causing this problem?