You checked this too? https://wiki.maemo.org/Debian-Tethering
I never used bt tethering, I always used a forwarded bt pan connection.
In principle you need to initiate a pan connection the rest you do with genwall. http://talk.maemo.org/showpost.php?p...5&postcount=62
Prerequirements for pan: [N900] /etc/bluetooth/main.conf comment out: DisablePlugins =network,input,hal