I see, you're having several problems with your Slingbox such as changing channels and and getting no good video. Below is a helpful link with steps on how to do a hard reset on your Slingbox.
Why perform a hard reset?
A hard reset wipes out all configurations, settings, and (usually) software updates from your Slingbox. After you perform a hard reset, you'll need to reconfigure your Slingbox again.
Sling Media Support