Thanks for posting in the forums! I'm sorry to hear you're experiencing issues with the quality of your audio and video when connecting to your Slingbox Classic.
If you are using Watch on Slingbox.com, it may be that you have hardware acceleration enabled. Disabling this typically resolves the issue.
Below is a link to an article that may help troubleshoot this issue:
Hope this helps!
The Sling Moderation Team