Hi,
you have to enable the PPTP protocol and the ports 8435-8438 in your router configuration.
On my router (Dir-100) I had to chose the additional rules for port forwarding tab.
There I had to chose "PPTP" then enter the IP of my PC and afterwards had to define the ports 8435-8438 as public ports and additionally set the 8435 as private port.
Besides that I had to define an exception rule im my windows firewall for the program "pythonw".
It's very difficult to guess, what router you use and how these setups have to be done on it.
So here's the most simple workaround for that:
Make a donation to the Altbierbude (include you login name in it) and fill in this form afterwards:
http://www.bierbuden.de/form/en/form.html
and within a few days you'll get ftp access which doesn't require all that configuring and is faster than the p2p access.
Regards
faderone