The video is out of sync with the audio in a presentation
From Avacast Support
The video is out of sync with the audio in a presentation.
Sometimes in Windows Media, the video will slow down and get behind the audio, then may speed up again to match the audio. If the system is unable to play media at its optimal speed, the system gives audio priority over the video, under the assumption (often correctly) that the audio is more important. This can happen if either your connection or computer system is not capable of playing the stream for any of the reasons described in The video or audio in a presentation cuts out, pauses, stops, or is choppy.
The situation can be aggravated if the presentation incorporates slides, logos or backgrounds that are in the Flash format and are not optimally designed (e.g. they contain lots of animation or text).
It can also be aggravated if the player window is very large. If you enlarged the window yourself, try reducing the size. If the Player window is already large when you open it, the Avacaster event coordinator may have selected one of the larger layouts (#7 and #8 in Avacaster 4.1, or it may be a custom layout)); you can try letting the coordinator know that the large layout is causing problems for you.
In all of the above cases, the situation can be even worse on older computer systems, particularly those with inexpensive video cards, small amounts of built-in RAM, slow processors, etc.