Corsair Vengeance 2100 on OS X
Are you using it wireless or plugged in? 

If you are wireless, I'll bet they're low on charge. If you look where the cord connects, it's likely blinking or solid red (which means you need to charge them).

As for the adapter, you don't need to keep un-plugging to reset them. On the left ear, you press the button for a few seconds. This will re-sync the headset to your USB adapter. If it correctly sync'ed, the blinking blue light on the adapter will stop blinking on stay solid.