Easy Connect is not available: Can't connect to the global peer-to-peer network

Can someone please help me as I'm about to pull out what little hair I have left.

Basically, the Easy Connect option in Windows Remote Assistance is available but it always fails to connect to the P2P network. I have been scouring the web for hours trying to resolve this issue, which was working last week.  These are the steps I've taken so far:

1. Configured GPO (set Teredo state to 'Enterprise Client' and enabled Teredo Default Qualified)
2. Installed Peer Name Resolution and Remote Assistance on the server
3. Enabled UPnP on the router
4. Uninstalled VirtualBox
5. Ensured that my PC is connected to one network only
6. Enabled public folder sharing

As I said earlier, this was working last week and the only changes I've made since then were to install VirtualBox, which I've now uninstalled, and to install Win8 on a seperate partition.

My PC is running Win7 Ultimate 64-bit and my router is a Netgear RangeMax 3300.

I thank you in advance for your help :)