I need help getting my Huawei E3131 modem to (consistently) work. I am currently running Ubuntu 12.04.2 and 3G dongles have worked many times before. However, my newly acquired Huawei E3131 is causing problems.

When plugged in, Ubuntu detects the device as a CD-ROM and a modem. I can browse the dongle's contents using Nautilus and Network Manager is able to configure and work the dongle out-of-the-box. I can even get to surf.

However, within minutes, the connection drops and the CD-ROM is unmounted. I wait about 15 seconds, then the CD-ROM mounts again and Network Manager is able to connect again with short-lived surfing. Rinse, lather and repeat.

It's strange that the device mounts as a CD-ROM, but works as a modem, too, suggesting that mode switching happens somewhere. It's not a signal coverage problem, either because I tested the same SIM card using 3 other different dongles (2 ZTEs and another Huawei) and it is only this E3131 that has this problem. If pertinent, the other dongles weren't being detected as CD-ROMs.

Output of lsusb

Bus 001 Device 002: ID 8087:0020 Intel Corp. Integrated Rate Matching Hub
Bus 002 Device 002: ID 8087:0020 Intel Corp. Integrated Rate Matching Hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 001 Device 003: ID 0ac8:c342 Z-Star Microelectronics Corp. 
Bus 001 Device 010: ID 12d1:1506 Huawei Technologies Co., Ltd. E398 LTE/UMTS/GSM Modem/Networkcard
Bus 001 Device 004: ID 0a5c:219b Broadcom Corp. Bluetooth 2.1 Device

I tried installing the drivers found here, but no fish. Furthermore, my device is an E3131, but lsusb for some reason detects it as an E398. I'm not sure how that plays a role for this problem, though.

I hope someone out there can help me. I'm out of ideas already.

Thank you very much!