This has now happened on 2 laptops I own, and only 2 that I have tried to optimize latency for...
 
The battery stops charging for some reason.
 
Now, when testing using Latency Mon, I usually go into device manager and disable the battery charger because it causes a lot of latency.
 
On my daughters Dell Inspiron 1545 and now on her Alienware 13 the battery stopped charging. The Inspiron was very old when it happened so I didn't think anything of it. Just a hardware failure. But the Alienware was only 2 days old. I'm sending it off for repairs.
 
I thought I'd ask generally whether anyone thought maybe I caused the problem by disabling it in Device Manager.
 
I have an HP laptop I've used for 7+ years that I disable the charger for and that has never been an issue.
 
Interestingly, with the Alienware, I can't even boot the thing plugged in! It's dead dead dead.

Try removing the battery and unplugging the power cable.  Hold the power button down for about a minute.  Then plug the power cable back in and press the power button.  This might get you running again to get any important stuff off the laptop.
 
I have the same problem with my Sager which is about 5 years old.

Thanks Dave.
 
To remove the battery in this PC I have to remove the keyboard. It's not a huge ordeal but a bunch of screws.
 
Since it's brand new, I thought I'd ship it back. It comes with a 1 year warranty. If it was at all easy to remove the battery, I would.
 
I'm tempted to try it anyway.

 
Geoff, when you say you disable the charger (didn't know you could do that), do you do it only for running Latency Mon and then you enable it again ?   How can your HP work without the charger ?  I've always thought that a laptop runs off the charger when plugged in (like a car runs off the alternator).

With laptops the Battery Management which you find in the device manager often needs to be disabled to stop the DPCLAT test from showing big spikes. Every laptop I've used for audio has been like that. 
I find just disabling the Battery management and the wireless is all that needs to be done to go in the green. 
  The battery management  app is for the notifications. It does not stop the laptop from charging when disabled. 
My Asus netbook still holds a charge good for 10 hours after 5 years. 
Two other older laptops won't run on battery for more than 5 min. All have been treated the same way, I just think some laptops come with crappy batteries.
My wifes Lenovo if you kill the battery stone cold dead is real hard to get it to reboot. You do have to remove the battery. This just happened an hour ago, the charger was unplugged.