Did you charge it using the wall socket or using your pc?
Since the original poster has not responded, might I ask about the difference I see when I use the supplied wall socket charger v. using my pc? The former charges my HD+, the latter doesn't appear to do so.
Your pc will charge the HD/HD+ but only when the screen is off. If you switch the screen on to check, it stops charging! You can check this out by plugging into your pc, checking battery %, turning off screen, leaving for an hour and rechecking battery %. It will have increased.
I asked the OP this because plugging into a wall socket using the wall plug is a stronger charge and is more likely to 'wake up' the Nook and charge it. The Nooks will only charge if they are switched on. If switched off when you plug into the wall socket, the Nook is woken up to charge and the pc charge may not be strong enough to trigger the wake up to allow charging.
Hope that makes sense!
Standard USB specification is that a source provides five "units" that can be distributed across up to four ports. A "unit" is 100mA. That means, if unshared, a standard port maxes out at 500mA (0.5A).
The Nook HD/+ charger is rated for 2.0A -- four times the current!
Some newer computers have "charger" ports. These can run higher current loads but typically only if the connected device does not activate the data lines (if the device sends any data signals the port activates current limiting). Some of these computers also have ports that stay powered when the computer is turned off (and may also be higher current levels -- my new Dell has a top access port with a lightning bolt icon next to the USB tree i in).
My TV has three USB ports. Two marked as 0.5A, the third labeled 1.0A HDD (meant to power a portable disk drive).
A standard 500mA port may not provide enough current to charge an HD, if the device takes nearly that just to run the charge monitoring software. A 1.0A charger may take two to three times as long to charge.