I have been encoding large number of videos to MP4 using the mainconcept HD h.264 coded in Sorenson Squeeze 5.0 using Mac Pro and Dell PC systems. The resulting MP4s needed to be able to HTTP stream when played in Flash 9 (or later version). To my surprise, only the MP4s encoded on the PC were able to http stream without problem. All MP4s encoded in the Mac Pro machine did not stream, instead the Flash player needed to download the complete file before being able to play it. I used Sorenson Squeeze 5.0 Pro in both machines (Mac pro with 2 quad cores running osx 10.5.4 and a PC system running Windows XP SP2) applying exactly the same settings and codeds on both, yet the resulting files turn out to be different as only the PC encoded files are able to stream. Anyone has encounter a similar problem?