I have one of those A1016, 1st generation, Apple Bluetooth keyboards, had it since late 2008, that will pair via bluetooth setup assistant, I can enter the passkey on the keyboard and I get the "congratulations your computer is now setup to use your bluetooth keyboard, message but, as soon as it is paired the keyboard accepts no input.
The problem started after I left the keyboard in my car overnight, and switched on, I believe, while the only macbook I had ever used the keyboard with was with me, 30 miles away. If I had not been in an extreme hurry at the time I probably would have thought to take the batteries out of the keyboard.
The battery level, currently, is at about 79%. The light on the caps lock key does not come on, but the green light on the on switch, underneath the keyboard, does seem to work, when I first switch it on that light blinks for a period of time.
Incidentally, the keyboard has been in this condition for a long time, now, and I deleted com.apple.Bluetooth.plist many times and I repaired permissions, even with "applejack" and with "iceclean", many times since the problem started.