Safari -vs- MobileMe -vs- .mp4 Video Streaming

So here's an odd one... I bought my wife a Flipvideo UltraHD for Christmas. We've played with it and gathered up a few .mp4 videos that we want to post now. The Flipvideo default file format is .mp4, and it plays just fine on all of my my Mac's desktops via Quicktime.app, etc... Anyhow, I go and drag it into iPhoto '09 and "share" it via MobileMe. Everything seems fine when uploading it. My family members with Windows IE 7 and 8 can view my posted videos from the MobileMe hosted site just fine. I can also see the videos just fine from the MobileMe gallery when I use Firefox 3.5.x. on my Macs. However, every time I try to access the videos via Safari 4.0.4 I get the error "Quicktime could not open the video. Please try again." My Safari Quicktime plugin is the standard 7.6.3 variety and I have both QT7 and QT10 installed on my OS X 10.6.2 systems. I removed and completely nuked QT7 and it's preferences, but that didn't seem to help so I reinstalled if from the SLeo DVD. Also, oddly enough, once I have successfully viewed the .mp4 using Firefox, the video appears to have been cached to my system, as Safari will then load the same video just fine. However, Safari will only load a .mp4 after it has been accessed with Firefox first.

Does this sound familiar to anyone? Any idea which Apple Quicktime is not working with the Apple Safari 4.0.4 browser?

Anyone...? Bueller...? Bueller..?