Not sure what happened here. I installed Cinnamon on my Ubuntu 12.10 environment yesterday, rebooted when finished and everything was working fine. I even used my WWAN modem after my fixed line broadband went down. However, after starting my machine this morning and seeing that my fixed line is still having problems (intermittently), I clicked the network applet and my WWAN device wasn't listed. It's not in the main network manager window either.

It is still present on the system, however:

$ lsusb
Bus 001 Device 003: ID 05ca:18b0 Ricoh Co., Ltd Sony Vaio Integrated Webcam
Bus 001 Device 004: ID 05c6:9221 Qualcomm, Inc. Gobi Wireless Modem (QDL mode)
Bus 002 Device 005: ID 04e8:6865 Samsung Electronics Co., Ltd 
Bus 002 Device 002: ID 0409:005a NEC Corp. HighSpeed Hub
Bus 003 Device 002: ID 147e:1000 Upek Biometric Touchchip/Touchstrip Fingerprint Sensor
Bus 008 Device 002: ID 044e:3017 Alps Electric Co., Ltd BCM2046 Bluetooth Device

Debug output from modem-manager, refers to a device that is blacklisted:

modem-manager[10186]:  [1355478137.024491] [mm-manager.c:866] device_added(): (tty/ttyUSB0): port's parent device is blacklisted
modem-manager[10186]:  [1355478137.024607] [mm-manager.c:875] device_added(): (tty/ttyS0): port's parent platform driver is not whitelisted
modem-manager[10186]:  [1355478137.024700] [mm-manager.c:875] device_added(): (tty/ttyS1): port's parent platform driver is not whitelisted
...

I couldn't see anything relevant in the debug output for network-manager, but I've created a paste for it just in case.

In /lib/udev/rules.d/77-mm-qdl-device-blacklist.rules, I found the following line that matches the device IDs from the lsusb output:

# Generic Gobi QDL device
ATTRS{idVendor}=="05c6", ATTRS{idProduct}=="9221", ENV{ID_MM_DEVICE_IGNORE}="1"

I tried commenting out the second line and restarting network-manager/modem-manager but it didn't help. I've no idea where to go from here, does anyone else have any ideas?