I just acquired a new Vodafone Mobile Broadband modem to replace an aging ExpressCard version I had that wasn’t working too well. It came in the form of a Vodafone-branded Huawei K4505 USB stick. It didn’t work completely out-of-the-box with Ubuntu 10.04, at first appearing unrecognisable. After some hunting, I discovered that these sticks initially present themselves as USB Mass Storage to allow you to install the Windows drivers. You have to give a few magic incantations on Linux to make them switch into modem mode:
Once the modeswitch command is executed, the USB stick will present itself as a modem and you can use the standard Ubuntu NetworkManager mechanisms to define your service provider and set up the connection. The stick should remember its state, and so you should only ever need the above utility (and command) once.