Try going into your internet security settings and lower the privacy level a little. I had to go from "block all cookies" to "high" to get mine to work.
It could be a proxy issue....
Go to Tools>Internet options>Connections>Lan settings. Check the “automatically detect settings” box and uncheck all the other boxes.
Go to Tools>Options>Advanced>Network>Settings then check the little dot that says: Auto-detect proxy settings for this network.
Make sure no other dots or boxes are checked. Click OK.
Then go to your firewall settings and make sure anything related to NOOK is Enabled.