ADDITIONAL INFO: I have two sound devices on this machine. The PCI audio card works fine - even the mic w/ skype etc. The only device that doesn't behave is the USB Logitech headset as described below. This device works fine under Window 7 so I know it isn't likely to be hardware or connectivity.
ORIGINAL: Mic works fine until it doesn't.
Noticed this first in Skype but then tried to debug in Audacity which shows levels are fine. This is the case until I start clicking in other applications at which point audacity eventually stops recording.
Tried disabling pulseaudio / restarting which had no effect.
alsa info can be seen here:
Very new to linux - any help greatly appreciated.