Why does the seekbar timing vary?

HI. I have a project that has been published and a slide that contains animations and an auto-play embedded MP4 file  (36 seconds). When previewed in Presenter and subsequently published and played back locally the seekbar shows a total time of 42 seconds and everything plays back fine. When I move this to a web server and play it back from there, it also shows 42 seconds and plays fine.

However, when my client tries to access this URL from work this same slide shows 36 seconds and cuts off before completing animations. If the client clicks in the seekbar the final animations will appear in the completed state. When the client does this same thing from their home computer the same slide shows 42 seconds and the slide plays properly. The client also noted a difference in seekbar total time on this slide depending if the course was launched from launch.html or player.html. The launch.html file adds more time in the seekbar.

My question is that I don't understand why the seekbar would be showing different times. If it published at 42 seconds and the presentation.xml file shows 42 seconds, then how is it possible that the seekbar can even show 36 seconds for some people?

Because the slide was seemingly cutting of just from some people I subsequently added a few more seconds to the slide using the sync animations feature. This resulted  in the slide completing properly. But again, I am not sure I understand the logic of flash timing/seekbar timing changing depending on how the course is accessed as I thought slide timing were "hard coded" when published.

Any thoughts or suggestions would be appreciated.

Thanks!

Stephanie