OK I'm sorry, I thought it is just a simple configuration problem what someone might identify by the error message.
If this is the wrong place for it I'm very sorry, than you can close this thread of course, I will start a new one at the right place (if I find it).
This shouldn't be a bug report, but a ask for help, so I will try to do what the how-to for bug reports tells me to now:
I'm running Tomato Firmware v1.28.8754 ND USB Std on a WRTSL54GS.
Tried this by start 3 times (erased NVRAM after every try): So I would say this reproduces the problem for me.
-Configured Router to have Internet.
-Installed Optware according to TomatoUSB-How-To on plugged devies
-Followed TomatoUSB-How-To to install pptp
-Followed last part of TomatoUSB-How-To to connect my Android Smartphone (Samsung Galaxy I7500 with Android 1.6) via pptp
(so the config files look exactely like in how to, if helpful I could paste them though)
cat /var/log/messages gives: micha.mytanet.de/wrtsl54gs/messages
other configs: micha.mytanet.de/wrtsl54gs/opt/