That could be caused by a number of things. More details are needed to assist.
Here's a good place to start:
- What Slingbox do you have
- What sources are connected to the Slingbox
- How are your devices wired together (what kind of cables)
- Does video work
- Have you tried watching from a different computer
- Has audio worked before
- Is the behavior consistent
Post back with additional information, let's see what we can do.