Comment 16 for bug 789508

Yes, I still have it. Constantly for example during bus rides to work. Also happens stationary, bad network signal quality seems to be affecting this. I think that also that if network utilization is high, the device is more likely to stay visible to the operating system and work ok. I don't know if Windows has this bug. It is however highly frustrating in Linux and rendering the device unusable for some. I have considered buying an alternative card to see if it performed better.

This happens in Kubuntu 12.04 LTS with kernel
3.2.0-31-generic #50-Ubuntu SMP Fri Sep 7 16:16:45 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux

This is what happens in dmesg when device (and network) disconnects:

[80790.192547] usb 1-5: USB disconnect, device number 39
[80790.193168] qcserial ttyUSB0: Qualcomm USB modem converter now disconnected from ttyUSB0
[80790.193230] qcserial 1-5:1.1: device disconnected
[80790.200470] qcserial ttyUSB1: Qualcomm USB modem converter now disconnected from ttyUSB1
[80790.200500] qcserial 1-5:1.2: device disconnected
[80790.200739] qcserial ttyUSB2: Qualcomm USB modem converter now disconnected from ttyUSB2
[80790.200775] qcserial 1-5:1.3: device disconnected

And this happens when the device comes back:

[80790.496243] usb 1-5: new high-speed USB device number 40 using ehci_hcd
[80790.631018] usb 1-5: config 1 has an invalid interface number: 1 but max is 0
[80790.631034] usb 1-5: config 1 has no interface number 0
[80790.636336] qcserial 1-5:1.1: Qualcomm USB modem converter detected
[80790.636876] usb 1-5: Qualcomm USB modem converter now attached to ttyUSB0
[80793.985067] usb 1-5: USB disconnect, device number 40
[80793.996588] qcserial ttyUSB0: Qualcomm USB modem converter now disconnected from ttyUSB0
[80793.996658] qcserial 1-5:1.1: device disconnected
[80794.776509] usb 1-5: new high-speed USB device number 41 using ehci_hcd
[80794.920269] qcserial 1-5:1.1: Qualcomm USB modem converter detected
[80794.920932] usb 1-5: Qualcomm USB modem converter now attached to ttyUSB0
[80794.922823] qcserial 1-5:1.2: Qualcomm USB modem converter detected
[80794.923284] usb 1-5: Qualcomm USB modem converter now attached to ttyUSB1
[80794.924829] qcserial 1-5:1.3: Qualcomm USB modem converter detected
[80794.925271] usb 1-5: Qualcomm USB modem converter now attached to ttyUSB2

Sometimes the device does come back onlne and sometimes it doesn't. I fix this by rmmod qcseril ; modprobe qcserial . If the module is in use, I just restart network-manager daemon, then reload the module.

TL;DR: The problem still exists in Kubuntu 12.04 LTS and kernel 3.2.0-31-generic.