I have two different mobile phones from T-mobile, a G2x and a Defy. Both are set up for wireless tethering.
I have two machines running Ubuntu 11.10, an HP netbook and an older Dell notebook. They will both connect to the signal from the G2x without any problem, but neither of them will connect to the Defy. It shows the Defy in my available networks, but when I try to connect it just runs and runs without connecting.
I also have three other Windows machines here in my home and they are able to connect to the Defy without any problem.
Is there a setting I can change or a command I have to run?
I used the Hotspot Mobile app by Motorola and with that I could connect to the Android wireless tether using Ubuntu. You have to configure the Hotspot Mobile app preferably setting a password and Ubuntu will recognize it immediately and let you connect. I used Defy with Android 2.2 and Ubuntu 11.10. If you still have problems, here is the Ubuntu official guide on connecting to ad-hoc networks.