Try powering the Nook down completely, and then starting it back up again, this will give it a reboot and may solve some of your issues.
The MP3 player on the Nook is very basic. I prefer my iPod. The Nook player sounds a little more washed out in the sound than the iPod, not as dynamic. I timed SBH on both at what should be 3:29 seconds. The Nook went to 3:35, so it actually did play the song slightly slower, though not enough that it should be an issue. My version was 256 kbps. Maybe if I used 128 kbps I would get a different result? Are you using variable bps MP3s?
I have had a few occasions where the Nook began acting erratically, but the shut down and reboot solved my issues. There is also a hard reset process that might work for you, but it resets the Nook to the original version 1.1 and wipes out your library, so you have to reload your books. If you continue having problems I would talk to tech support first, and then pursue an exchange, regardless of whatever the warranty is.
One advantage of e-readers is that you can load them up with non-copyrighted works, pre-1920's, somewhere around there, for free. Google books has a large library of these books available for a free download.
"It will take an amazing amount of control,” she mused. “More even than Carlisle has. He may be just strong enough…the only thing he’s not strong enough to do is stay away from her. That’s a lost cause.”