Thanks for your answer.
I suspect it’s more complicated than that, because also noticed a sound problem: sound is completly out of sync (see Variable sound drift when playing MP4 in VOD application).
The file plays perfectly when using http progressive download, and shows the sound problem problem with wowza’s test players (sorry my description was wrong in my first post).
I noticed that the sound is also jerky on the ipad, so I suspect something related to the file encoding: maybe some weird incompatibility between wowza and the tracks multiplexing?
greg