I have the exact same problem
I have connected the cables as per the manual and I allowed the slingbox PRO to download the latest firmware.
I have tried viewing it on my PC at home, webviewer, slingplayer and on my iphone4 always the same black and white video with no audio.
I have a pretty fast broadband connection at home and I am no more than 5 feet away from my rooter when trying to access from my iphone4
I really want to get this problem sorted by Tuesday as I'm going away for Christmas and wanted to watch my TV while I was away for two weeks, the only reason I bought the SBP.