LOL The more I use it, the more I realize how troublesome it really is...
I find the keyboard connects without incident every time so far, it's the mouse that causes the problem. The issue seems to be when the system loads the mouse pointer. This has worked the most often for me; just nudge the mouse so it initiates the connection. Once I see the BT status icon indicate a link, I change the desktop page before I move the mouse. Then once I nudge the mouse again, the pointer usually appears in the top left corner. Once the pointer is loaded, it seems to work trouble-free.
Just thought I'd tack this on instead of making a new post:
This seems to be a fool-proof way to connect the BT mouse and assumes you've already paired the mouse; first enable Bluetooth on the Nook, and allow it to initialize. Connecting the mouse too early will likely lock up the GUI. Once the BT icon is present in the status bar, nudge the mouse or press one of its buttons. This should initiate the link between the mouse and Nook without actually telling the Nook the pointer has moved. This seems important, because if the Nook registers movement before the mouse pointer appears, the GUI will likely lock.
After you've coaxed the mouse to open the link, the BT status icon will change to indicate a link. Once this has occured, swipe your desktop left or right to change screens. Once the screen has changed, and any animations have finished, nudge the mouse again. The pointer should appear on the top left corner of the screen. If you move the mouse without moving the screen first, the pointer won't appear and the GUI will lock.
Once the pointer has appeared, there isn't much issue. The keyboard has no trouble connecting at any time.
And as always, YMMV.