I have not had any problems before but just this week when I try to watch my slingbox on my WDTV Live player or on my computer all I get is audio when I try to play in HD. When I play it in SD I get audio and video just fine. I have not changed any settings in software or hardware. I have had my Slingbox PRO_HD for a few years with no problems. Any ideas?
My first thought is to reset your router, WDTV and Slingbox.
Often this resolves issues such as what you are describing.
This article: How to reset your Slingbox to factory settings walks you through the process.
Let me know if this resolves your issue