Some Huawei modems, such as the E220, first exposes to the kernel usb-storage mode then switches to usb-serial mode, without the kernel being able to follow as well.
But someone ( I jsut remember is German and keen to assist) patched the kernel to enable it to switch mode.
I know it is now included in default installation of RHEL 6.x (and clones) as well in Fedora (I think from 14 and up) as udev rules.
So I guess that you are using an old kernel version.
But you better share with us more details about your environment.
Last edited by tshikose; 11-16-2012 at 08:39 AM.