To start with. Verify the port number you are using in MC and make it sure is the same port as you forwarded in your router. Also verify you are forwarding to the correct IP address.
After that look at Windows Firewall and/or any other software that might manage your firewall. I use ESET Smart Security and some times it is a pain in the ass to get a proper filter setup and I still have to manually correct the windows firewall (which it manages).
Input your servers LAN IP address and port instead of your media key. example: 192.168.1.199:52199
If you can connect to your server through Gizmo by doing that, then something is wrong with your router and/or firewall.
If you still can't connect, could be a local firewall or other media center configuration issue
Also possible Gizmo may be messed up. You could try deleting its local Cache under Androids App Management, or even try uninstalling and reinstalling it, I suppose.