bluetooth assistant missing - keyboard won't connect

Keyboard and mouse died after the 2007 iMac went into sleep mode. Happened before so I disconnected the batteries, trashed the bluetooth preferences, restarted etc. Only now the mouse works but the keyboard will only connect for a few secs. Worse, it tells me that Bluetooth Setup is missing, know I did not delete that. Is there a way to download and install it? Shouldn't it rebuild preferences?

all help appreciated. thanks.