This example is for Chalmers PPTP VPN.
Server: vpn-gw.chalmers.se

1. Install network-manager-pptp.

sudo apt-get install network-manager-pptp

2. Add a new VPN connection in Network Connections. Choose PPTP, create.
3. Add the following and only the following

Gateway: vpn-gw.chalmers.se
User name: NET\your-username-here
Password: your-password-here

Click Advanced...
In Authentication, select only
CHAP
MSCHAP
MSCHAPv2

In Security and Compression select all and
Security: All Available (Default).

4. Restart your computer. This is important, don’t miss out on this one.
5. When back in Ubuntu, connect to Chalmers VPN, then click Deny when it asks
about the keyring. Enter your password for your account and then select Always Allow
when it asks about the keyring the next time.
6. Done!

Why all this restarting, denying, re-entering passwords and stuff you ask? It seems like there’s a bug in network-manager-pptp which will hinder you from connecting if you don’t follow the above procedure. Don’t ask me why this bug isn’t fixed, but I don’t think doing the above steps are that gruesome in order to get the simple functionality of an otherwise well-working VPN GUI for Ubuntu.