I am having the exact same issue. I haven't used my slingbox in 9 months. Never a problem before. Got it set up again and works fine in the home, but not outside the home. I also initially had the audio problem as well. What I had to do is use the S-video cable for video and then the red/white ports of the RCA cable where I matched up to the two audio out ports on the back of our Comcast DVR. For some reason using the actual RCA cable ports on the DVR didn't work. Not ideal, but the sound does work. Still can't solve viewing outside the home though.
Hello Jmcd & Ahageman,
The following links will allow you to get all the information about the Internet Viewing setup,
Let us know how it works.