You posted here using your Sling account, so your internet connection and Sling Account credentials are apparently working. Ha !
This smells like a security settings problem to me, something on your machine is blocking you because it doesn't like the connection you're attempting. I can't say for sure that's it, but it seems likely.
Try using the full SlingPlayer for Windows, see if that gets though. If not, post back and let's see if we can figure it out.
One big difference In windows 7 is network location
When you installed the slingplayer you might have done so in a Home network location However later you changed to a Public network location and didn't allow the slingplayer to connect to the internet here is a link on setting your network location.
Here is the pop up
Many new laptop come with some kind of firewall software installed check that as well.