I went to this site and saw the still photos. It is obvious that there were two cameras. However it is not an 11 hour time difference. The camara with the 2:40 approx time stamp shows one of the holding up the severed head. The one with the 13:00 approx. time stamp shows the decapitation process so the best conclusion is that one of the cameras had the time wrong OR one of the cameras was from outside of Iraq and different time zone. http://pictures.albawaba.com/nickBerg.html
I had stopped watching the video after his head had been completely severed and removed. I did not need to watch them defile his corpse.
Since the camera one contains the angle used to show his head being held high (and then it cuts BACK to camera 2 for the shot of his head in his lap) it is very clear that there are 2 cameras.
My first response when I saw the video (and the screams went out of synch) was that after 5 minutes of arabic, I was in no shape to tell if the sound had gone out of synch or not. If you do not have the proper codecs installed and you are viewing video files, you can get jerky motion, sound synch problems, audio with no video, video with no audio, etc.
Also if you do not have good compression, you can get sound synch problems.
It was obvious from the get go that they were not using digital camcorders (which would have aided greatly in publishing this video to the web).
I don't say this to be morbid or to have an aire of detachment. I say this because they were my logical observations. As I say, I care enough that I didn't watch every second of the video (I still haven't run it a second time).
If the networks HAD aired the full video, there would be far less speculation about "why the clock jumps" (everyone would see it jump back to the proper time).