MS Bluetooth Notebook Mouse 5000 loses connection

Operating System: Mac OS X 10.5 (Leopard)
Processor: intel

I have a Microsoft Bluetooth Notebook Mouse 5000 which is supposed to work
with my MacBook Pro laptop. But it seems to constantly lose connection when
the laptop is idle for an hour or so. Simply moving the mouse or clicking
the buttons more often than not has no effect. I often has to rediscover
and re-pair the mouse with the laptop in order to get it to work. In
addition, I can't find any drivers to allow me to map the buttons. This is
supposed to be a "Mac" mouse, but it's not meeting my needs very well.