PPTP server on Ubuntu 12.04

PPTP server on Ubuntu 12.04

I'm trying to install a PPTP VPN server on Unbutu 12.04 from Linode. I've
followed this guide:
http://silverlinux.blogspot.co.uk/2012/05/how-to-pptp-vpn-on-ubuntu-1204-pptpd.html
I've copied each command exactly (copy pasting mostly) and my server seems
to accept my username/password after I've set up the VPN under Windows,
however I'm then greeted with this: http://i.imgur.com/QflNdhh.png
At first I thought it was a firewall issue, however it seems my firewall
is set up to allow all connections by default. The output from sudo ufw
status verbose is:
Status: active
Logging: on (low)
Default: allow (incoming), allow (outgoing)
New profiles: skip
To Action From
-- ------ ----
22 ALLOW IN Anywhere
1723 ALLOW IN Anywhere
22 ALLOW IN Anywhere (v6)
1723 ALLOW IN Anywhere (v6)
and it even happens if I run sudo ufw disable, so it can't be a firewall
issue, can it?
Has anyone experienced this problem before and knows how to fix it?