I have a rooted and unlocked Samsung Exhibit II 4G, which I am using on the AT&T network. When I used this phone on T-Mobile, the provided tethering app worked OK, but now that I'm on AT&T, the same tethering app aborts with an "Invalid SIM card" message. I've tried using Barnacle, Open Garden, and "Wireless Tether for Root Users" without success. The closest I've gotten has been with Open Garden, where the client (Windows XP) connects to the phone, and a DHCP-issued IP address is assigned to the client, but not even a ping gets through. Barnacle connects, but I get the 169...etc IP address that Windows runs to when it can't get an address. Also, if I shut Barnacle down, then try to startup again, startup fails. In order to use it again, I must reboot the phone. Halp!