This could be caused by a multiple of reasons. I would recommend checking to make sure that everything is up-to-date.
This article below can further explain what to check to fix this issue:
Sling Media Moderation Team
Thanks for the ansver - but it does not help.
As mentioned my cable-box works fine directly connected to tv.
Using compoite-cables audio and video are in sync.
Using HDMI to get a good video signal audio is not sync.
May I suggest a possibilty to adjust in the slingplayer software - maybe the same way as in XBMC?
I am having similar problems with my HD-Pro. The link referenced above (http://support.slingbox.com/get/KB-5000345.html) no longer works. The download bit rate is in excess of 6000 kb, so there is plenty of bandwith,
What settings can be adjusted to correct the sync problems?