Tethering setup disappeared

[Sergiomiami]

My iPhone 3G 4.1 has jailbreak for a few days and was working OK (I mean slow but OK) until I try to install my Wi with Cydia. I could not have it work, but no big deal I removed it. Now, thethering setup page disappered from the settings. I tried to restore with original firmware 4.1 but nothing came back. I did JB again but nothing new. I tried to reinstall tethering (downloading from BenM..), it says it can accept only one APN configuration at the time (if I understand it, it means I already have tethering...but where).
I am stucked.
Any help is welcome.