I've been having Bluetooth problems on my Mac mini (mid 2007) since I tried using it with a Bluetooth keyboard and mouse; the symptoms were random disconnections and, some time after, either a few seconds or minutes, reconnections.
Lots of people seemed to be having this problem, but nobody really seemed to get to the bottom of it. Some people on the internets suggested this might be overheating, and suggested smcFanControl which is a nice little app, but didn't really help in my case.
Eventually I gave up, assuming it was a hardware flaw, and purchased a USB Mighty Mouse and keyboard; this worked fine, but recently my Mighty Mouse gummed up for good (and I broke it cleaning it, duh!), and, after the release of Lion with it's iOS scrolling and gestures etc., I purchased a Bluetooth Magic Mouse, and lo, the problem came back; starts pretty soon after start-up, even when the temperature is only in the high 40s (°C).
I’d also noticed that, without any Bluetooth devices, the Growl hardware notification system frequently reported USB disconnects and near-instant reconnects; effecting all USB devices and even wireless networking. It didn’t really cause me any problems, and I kind of assumed it was normal, under-the-hood stuff (like when plugging in an iPhone or Camera always caused read errors on my external USB drive!).
However, I’ve just tried tinkering with the Bluetooth-PDA-Sync thing, as A Velerez mentions in the comments of this post, except in my case, I just switched Bluetooth-PDA-Sync off, and it seems to have fixed my Bluetooth disconnection problems (yay!). The random Growl hardware disconnection notifications have gone away too.
Could this be something to do with having once used a Palm device to sync over Bluetooth? Is everyone else experiencing the problem, without finding that the fan control fixes it, a former or current Palm user? Is the Bluetooth-PDA-Sync even a Palm thing, or a generic OS feature?
Anyway, assuming you don’t need it, switching Bluetooth-PDA-Sync off seems to fix this problem, assuming you’re not frying your hardware too…
Mac OS X Lion 10.7.2 (11C74)
Mac Mini Mid 2007
2 GHz Intel Core 2 Duo
Mac Mini Mid 2007
2 GHz Intel Core 2 Duo