I understand you are unable to connect to your Slingbox 350 from your SlingCatcher. The reason for this is simply due to the fact that the Slingbox 350 and 500 models are not compatible with SlingCatcher and therefore shouldn't be accessible.
This incompatibility is mentioned in the article:
If you are looking for a device to allow you to stream your Slingbox 350 onto another TV, then you would want one of these fine "Connected Devices":
Hope this clears things up!
Sling Media Forum Moderation Team