Try doing a full shutdown / power on -- hold in power for ~20 seconds, ignore the shudown dialog and keep holding the button. Once it's off, hit power ~5 seconds and it will come back on.
On the charging issue: what color is the N on your charging cable? My NC needs to be left alone while charging - the contacts are hinky and if I move it when charging, it can very easily go in and out of fast charge (orange) to "I'm done" (green) or to no charge (no color on the N)
If the N was orange overnight and you're only at 51%, there's an issue. Is the device new to you, new from BN, refurb?
The power cycle may help with the charge, though - there's some involvement in charging from the OS, and possibly if it was running with the error up all night, it wasn't picking up charge correctly? (and it can mostly run, except for the screen, while appearing to be asleep.)
Had this DRP open failed problem too from time to time. It indicates a problem in the downloaded book file. An easy way to usually clear it is to archieve the offending ebook and the immediatly unarchieve it.
This will force the Nook to re-download the ebook file, and usually corrects the problems.