Hi,
In fedora 11, I have problems with the Huawei E220/E270 3G USB stick (vendor 12d1, product 1003). As I have learned, the problem seems to be with the NetworkManager. Here is the relevant debug info:
There's issues with the E220 if it has an older firmware. There was some bug where it essentially kept cycling through modes. You might want to check that you have a late enough firmware on it.
Peter