Yeah same problem. Both with a wired USB Lync compatible headset. I've been struggling to get it working with Cisco Softphone. Also have a wireless Plantronics headset that exhibits the same problems.
Came up with a workaround today. Keep your headset connected to the host machine and then configure it as your default sound device. The unfortunate side effect is that all audio will now play thru your headset. In this fashion, I've got it working, so can finally make calls via my softphone and not have to resort to my mobile and suck my free minutes, which isn't funded by my work place.