Funny you should mention this - discovered today whilst restarting etc to get wireless keyboard woken up. You can turn off Bluetooth using menu bar icon but then cannot use the same method to turn it back on. What you have to do is launch System Preferences, then launch the Bluetooth dialogue - in the dialogue next to the big Bluetooth icon is a tickbox called On. Click on it to put a tick in it and you are away again. A rubbish approach but it seems to work until the problem is fixed.
Don't know about anybody else but Leopard seems to be going down hill, failing to fix the things that make it a backward step from Tiger. If I had the time would put Tiger back on and put L down. Wished I had never gone there.