Apple Wireless Keyboard will not become discoverable--solution
Not so good, because I soon realized that the keyboard wouldn't go into discoverable mode. Pressing the power button caused the light to glow for a few seconds--indicating the batteries were still charged--but it wouldn't blink. I tried removing the batteries, inserting new ones, all to no avail. Just kept pressing the button, getting the glow without blinks, and the keyboard wouldn't show up in the bluetooth setup list.
So I guessed that the keyboard still thought it was paired with the computer, even though the computer knew it wasn't. And then I read somewhere that the range for the keyboard was around 30 feet or so. So I walked out of our cubicle area and into a stairwell 50 feet away. Sure enough, after the initial glow, the light blinked! It was discoverable.
I ran back to my desk, hit "continue" in the bluetooth setup panel, and paired the keyboard again.
So, if your keyboard isn't paired with your computer, but still won't go into discoverable mode, maybe this trick will work for you.
MacBook Pro (early 2011); iMac (20-inch Mid 2007), Mac OS X (10.6.7), Wacom Intuos 3 tablet; HP Deskjet 6840; iPhone3GS