Well I'm at the stage now where I have three 5.6U e-smith boxen.
two will /sbin/modprobe ip_nat_pptp just fine.
The one I actually want to use gives all kinds of rubbish and can't load either nat_pptp or contrack_pptp, specifically unresolved symbols and a GPL license problem. I don't understand this at all!
Any offers of help would make me jump up and down with glee.