(In reply to Joachim Ziebs from comment #13) > (In reply to Bruno Pesavento from comment #12) > > Well, actually none of the abovementioned ideas helped. OK thanks; so apparently my laptop and/or my e156G have timing problems that cause conflict between the "option" and "usb-storage" drivers. Accordingly, my fixes should be considered as configuration-specific. But looking at your dmesg: [100742.631145] usb-storage 2-4:1.0: USB Mass Storage device detected [100742.631549] option 2-4:1.0: GSM modem (1-port) converter detected [100742.631845] usb 2-4: GSM modem (1-port) converter now attached to ttyUSB0 [100742.632083] usb-storage 2-4:1.1: USB Mass Storage device detected [100742.632497] option 2-4:1.1: GSM modem (1-port) converter detected [100742.632783] usb 2-4: GSM modem (1-port) converter now attached to ttyUSB1 I still wonder how "option" and "usb-storage" engaging the same ports might cause no harm in your case.