Updating to OS X 10.7.4 has caused Bluetooth problems for many people, both with Bluetooth keyboards/mice and audio devices. If you find that Bluetooth stops working after applying the update, try the following one at a time:
– Disable and re-enable Bluetooth (may require using a wired mouse if your Bluetooth mouse is the problem)
– Unpair your device, reboot, then re-pair your deice
– Download and re-apply the OS X 10.7.4 combo update