Try the troubleshooting in this article to see if you can figure out the issue (https://community.sling.com/message/8730#8730)
You can test the corresponding output cables from the Slingbox. They're simple pass-through cables so you can plug them into a television to observe what the SLingbox "sees" and "hears"
Did something change in the sling software that could have caused it?
Nope, unless you inadvertantly made manual options selections.
Any suggestions on areas to check? Currently in the back I have both component and composite video hooked up. Just no sound using any device- Mac, Ipod, or blackberry. Very frustrating because it used to work great!!!!
The Slingbox can only rebroadcast what it "sees" and "hears". First part of the troubleshooting is to determine what it "sees" and "hears". The rest of it should be able to troubleshoot from this post. (https://community.sling.com/message/8730#8730)