Has anyone managed to get a PPTP dial-in VPN working from an Android 2.x phone to a 2830 (or 2820)?

I've set "Allowed Dial-In Type" to PPTP and that's about all other than username/password on the 2830, and on the Android phone done "Add PPTP VPN" and have tried both "enable encryption" on and off, neither works.

When I try and connect the phone thinks for about a minute ("connecting...") then states "unable to connect to the network" - no useful information. I've tried external to my LAN over 3G (turning off WiFi when trying it at home).

Thanks