I also had this problem... the actual problem is with N900.. not with any carrier.. i used to get this "cellular network not available" error whenever i tried connecting to gprs or 3G.. but i noticed that, when i keep one of my "conversations thread" open.. i can connect to the gprs / 3G. maybe the problem is with the firmware.. i re-installed the firmware and it connects now. isn't there any way to correct the problem without flashing again??? :O :O :O