I had never heard the buzzer before, and it took me a few minutes to realize it was my DNR202L. So, I logged into the DNR202L configuration page, to see that there was 0% free space left on my hard drive (which is bizarre because I had it configured to reclaim space, and it had been working fine for some time). I clicked on restart system. Thankfully the buzzing stopped, but it has been hung on the rebooting screen for 20 minutes now.
Suggestions?