Yesterday i upgraded my ubuntu 11.04 to 11.10.
Everything gone great but after restart, my modem was not able to connect
with the system.
Error was "Modem Disconnected, you are offline now."
I resolved this issue with following steps
1. Click on Network Icon
2. Click on edit connection > Mobile broadband > select the network(tata photon in my case)
3. Go to Edit then again click on mobile broadband
4. Then Fill data like : Number =#777 Username = internet Password = internet.
5. Save it. Then it was automatically connected.