I use a Capitel 3G EVDO USB CDMA modem (device id - 1c9e:9e00)to connect to the internet. In previous versions of Ubuntu, 11.10, 11.04, 10.10, when I plugged the modem into the USB port, after brief time Network Manager would list it in the Network Manager list as Configure New CDMA modem and the I could configure the modem with its username and password and use it normally.
After I installed Ubuntu 12.04 Precise, the modem is probably detected because it does show up as Omega Technology, device id ic9e:9e00, when I type 'lsusb' in the terminal. But Network Manager does not display the modem in its list even after a long period of time. If I try to create a new Mobile Broadband connection, the new connection dialog box does not display any supported device.
This is a somewhat widespread problem of 3G modems not being detected with Ubuntu 12.04, whereas it worked perfectly well with the previous versions and apparently there is no clear solution to it yet.