USB headset cannot be selected in settings on 1st plugin

I am running Ubuntu Quantal (12.10). I have Logitech USB headset. The firts time I plugged it into a USB port, the System Settings/Sound/Output panel immediately showed the device and allowed it to be selected. However selecting it did not change the flow of audio, which was still emitted from the internal speakers. Also, closing the settings panel and opening a new one showed both devices but had the internal speakers selected. So it seems to me there are two problems:

a) The settings panel is failing to set the default sink in PulseAudio, but not detecting the failure or not handling it, e.g. with a visible error message.
b) PulseAudio does not automatically switch to the USB headset when it's plugged in.

Following "advice" on the Internet, I found the following workaround:

1. remove or move aside ~/.pulse/probably two bugs:
2. leave the USB headset plugged in
3. log out and log in again

After this, I can plug the headset in and successfully manually select it for output and input using the settings panel. It's still not automatically becoming the default. So this works around problem a) not problem b).

The headset appears in lsusb as

Bus 001 Device 021: ID 046d:0a01 Logitech, Inc. USB Headset