I've had two die like that and Plantronics has been good enough to RMA them for me - great and all, but I count on my UC Bluetooth headset for work all day every day.
Today, it happened again - but this time I found a post in the Plantronics forum with detailed steps to ressurect your blue-light flashing dead Voyager Legend!
I called technical support just now! He said I need to reset it and it worked. Like this:
1. Turn off your headset.
2. Press and hold both Call and Mute buttons at the same time.
3. While pressing these buttons down, turn on your headset.
4. You should see the LED on the headset flash blue and red alternately.
5. Turn off your headset.
6. Turn it on again. You should hear the female voice giving the headset status.
Took 30 seconds or so for the red and blue lights to stop flashing and then it worked again for me! Wanted to share this excellent tip on fixing your Plantronics Voyager Legend UC headset!