Heya, I have this immensely peculiar problem.

I've got two Arch Linux machines using this pptp tunnel with no problems, I wrote a small script to call the pptp utility (pon) and set up routes - and I've copied the entire folder /etc/ppp over from one of the Arch machines to Ubuntu in order to replicate every setting used.

However, the Ubuntu machine cannot connect at all. Below are the logfiles captured. One for a successful connection via an Arch Linux machine, the other is a connection attempt from the Ubuntu machine.

Logfile from one of the Arch machines (ie. a successful connection)
http://pastebin.com/f5a058b58

Logfile from the Ubuntu machine (the one that cannot establish a connection:
http://pastebin.com/f587f7da8

I'm really hoping someone here can spot something, because I've been wrestling with this for days on end and I just can't figure out what's missing on the Ubuntu machine.