Thanks for posting this in the forums! I'm sorry to are unable to connect to your Slingbox 500. If you are referring to the desktop SlingPlayer, it is no longer supported. However, it will work with any Slingbox model starting from the Slingbox PRO-HD to the Slingbox Classic.
The desktop SlingPlayer will not work with the Slingbox 350 or 500. It is only supported in Watch on Slingbox.com. I do apologize if this has been any inconvenience to you.
Below is a link to an article from our knowledgebase that tells you what SlingPlayer software works with each Slingbox. The desktop player is referred to as Older SlingPlayer Software in the article.
Hope this helps!
The Sling Moderation Team