I've been having the same problem, since the 10.5.7 upgrade - my bluetooth mighty mouse stops working 2-3 times a day. Weird thing is my bluetooth apple keyboard works fine during such mouse dropouts.
I still haven't figured out if any events cause the mouse to stop working, or if it's plain random. The only way to bring the mouse to work again is by turning my MBP's bluetooth off/on. Batteries are fine btw... has anyone figured this one out?
I have this exact same issue. 2-3 times a day, sometimes 10-12 times a day. Mouse batteries are at full.
When the connection drops, I simply click the mouse a couple of times and it comes back, only to lose the connection again soon.
It's frustrating, especially when you are clicking something and it just hangs.
I'm running a MacBook Pro 15" 2.66 with 10.5.8. The Mighty Mouse also did the exact same thing on my older MacBook Pro 15" 2.0ghz running Tiger and Leopard.
I say it's the mouse, but I don't have another BT mouse to test with.
FWIW, this is the only BT device that drops off. Keyboard, BT headset and PAN for cell phone never drop.
I've tried making the Mighty Mouse a favorite, which was suggested by someone. That curbed it for maybe a day. Then back to connection lost messages popping up.
The resolve to click and have it reconnect is easy, but frustrating none the less.