Bluetooth apple keyboard won't connect

Yesterday I had the spinning beach ball of death. I had to do a hard shut down. Upon restarting, I was faced with the grey screen only. Couldnt log on, it just hung there. I couldnt boot in safe mode. Also tried resetting VPRAM but wouldnt do anything from what I could see. Gave up thinking I had lost all of my newborns photos.

Today I turned it on and the bluetooth setup assistant was on the screen, it was hanging up my system I think. I tried to login, but it would not recognize my keyboard. I had to hunt all over town, get a new keyboard that was USB input, and then was able to log in. Still, my keyboard is undiscoverable. I put new batteries. I press power, green light comes on a few seconds, then goes out. I press a key (as suggested). Still nothing.

I was able to at least get logged in however, and running time machine as I type hoping to not lose anything again.

How can I re pair my apple bluetooth device to my imac?

Note: imac is OS X 10.6.8.