Has anyone else experienced this? After my iMac has been sleeping for a while, pressing the spacebar on my Bluetooth keyboard causes the machine to wake up like expected but it doesn't allow me to start entering a password for what seems like a very long time, then the keyboard will flash a green light LED and then all seems fine. The batteries are new so that shouldn't be the cause. It's the only thing that's really annoying me about my otherwise perfect machine. Maybe I'll try to un-pair and re-pair it to see if that makes a difference.