Several users are reporting issues regarding a lack of consistent connectivity when using their Bluetooth Might Mouses. The issue appear to be related to firmware updates from Apple.
"Ever since I updated my bluetooth firmware to the latest version, I've noticed that for no reason, mighty mouse will stop responding. I have to turn off bluetooth, then sometimes, switch off my mouse, then switch it back on. Then it works again. I know I read another post where people had the same problem, but I wasn't experiencing it then.Although no official solution from Apple has been found, users in this ASD forum thread suggest turning Bluetooth off and on again, leaving the Bluetooth preference pane open, and connecting a wired mouse and trashing all Bluetooth devices and preference files. Other users in this forum suggest these approaches either do not work or only temporarily restore connectivity.
My batteries are fresh, and this started happening with the new firmware, so I know that's the cause, or some other hardware issue that came to light with the new firmware."
As always, if you are attempting to troubleshoot this, or any issue that involves trashing preference files or manipulating root level items, be sure to have a stable backup of your important data. MacFixIt will be sure to keep you updated if and when this issue is resolved on an official level.
Are you having this problem? Do you have a workaround? Let us know in the comments!