can't shut down or restart macbook pro

If I choose restart or shut down from the apple menu the icon for my hard drive disappears and it looks like the finder has quit, but nothing more happens. I can bring everything back by simply choosing the finder in the dock.

It got to this state after I connected a nook ereader via usb. I found that I could not eject the nook. After spending nearly an hour on hold with B&N customer "service" I decided just to unplug the thing. Of course I got the message warning of possible serious harm, but the nook seems to be ok. At first there seemed to be sort of a phantom nook still connected. I got the message that the nook could not be ejected because it was in use, but by a series of steps that I probably can't reproduce, I got rid of that message. The MacBook seems to work fine except for this little problem of not being able to restart or shut it down. Eventually I'm going to need to do one of those things to, e.g., install new software. So I would like to resolve this problem.