Why won't my wireless mouse connect to Bluetooth?

Question

My Bluetooth-operated mouse, which I've been using for at least 6 months, has stopped working on my iMac (2009 version). It simply lost connection from one second to the next, and I haven't been able to reconnect for weeks. (And yes, I put new batteries.) I know the Bluetooth on my computer is fine, because my wireless keyboard and speakers are connected just fine via Bluetooth. I tried turning the mouse off, and then on a few minutes later. I also tried turning off Bluetooth on my computer and then turning it back on in an attempt to "reboot" it. I also tried restarting the entire computer. I also opened Disk Utility to "verify and repair" disk in case there was any damage of some sort that was causing the problem. And when I went to test the mouse itself on a different computer (which is one of the older version iMacs that are plastic white and thick and have a smallish screen), the mouse connected to the Bluetooth there and worked perfectly. It's been very frustrating to use an older mouse with a short cord and the little ball-scrolling-thingie that doesn't work when I scroll down, only up.
When I try connecting the mouse to my iMac, I get one of two results. 1) Up until right before I submitted this question, the Bluetooth settings showed that the mouse "connected" but there's no response on screen when I move the mouse. After 5 or so seconds, it says "disconnected". 2) More recently, when I try pairing the mouse, it doesn't even connect at all anymore. I get the small yellow exclamation-mark-triangle error message, saying it can't connect to my mouse. What can I do, short of buying a new mouse? These wireless mice are too expensive, and I'd really like to resolve the issue with this one.

Answer 1

How to Reset Your Mac's SMC
The method for resetting your Mac's SMC depends on the type of Mac you have. All SMC reset instructions require shutting down your Mac first. If your Mac fails to shut down, try pressing and holding the power button until the Mac shuts down, which usually takes 10 seconds or so.
Mac portables with user-removable batteries (MacBook and most MacBook Pros):
  1 Shut down your Mac.
  2
  3 Disconnect your Mac portable from its MagSafe connector.
  4
  5 Remove the battery.
  6
  7 Press and hold the power button for at least 5 seconds.
  8
  9 Release the power button.
  10
  11 Re-install the battery.
  12
  13 Reconnect the MagSafe connector.
  14
  15 Turn your Mac on.
Mac portables with non-user-removable batteries (MacBook Air and some late 2009 MacBook Pro models):
  1 Shut down your Mac.
  2
  3 Connect the MagSafe power adapter to your Mac and to a power outlet.
  4
  5 On the built-in keyboard (this will not work from an external keyboard), simultaneously press and hold the left shift, control, and option keys while you press the power button. Release all keys at the same time.
  6
  7 Press the power button to start your Mac.
Mac desktops (Mac Pro, iMac, Mac mini):
  1 Shut down your Mac.
  2
  3 Unplug your Mac's power cord.
  4
  5 Press and hold the Mac's power button for 15 seconds.
  6
  7 Release the power button.
  8
  9 Reconnect your Mac's power cord.
  10
  11 Wait five seconds.
  12
  13 Start your Mac by pressing the power button.
Alternative SMC reset for Mac Pro:
If you have a Mac Pro that isn't responding to the normal SMC reset as described above, you can force a manual SMC reset by using the SMC reset button located on the Mac Pro's motherboard.
  1 Shut down your Mac.
  2
  3 Unplug the Mac's power cord.
  4
  5 Open the Mac Pro's side access panel.
  6
  7 Just below the Drive 4 sled and adjacent to the top PCI-e slot is a small button labeled SMC. Press and hold this button for 10 seconds.
  8
  9 Close the Mac Pro's side door.
  10
  11 Reconnect your Mac's power cord.
  12
  13 Wait five seconds.
  14
  15 Start your Mac by pressing the power button.
Now that you have reset the SMC on your Mac, it should be back to operating as you expect. If the SMC reset didn't fix your problems, you can try combining it with a PRAM reset. Although the PRAM works differently than the SMC, it can, depending on your Mac model, store a few bits of information that the SMC uses.
If you're still having issues, you may wish to try running the Apple Hardware Test to rule out a defective component on your Mac.
Resetting the Parameter RAM
One easy fix for many issues is to simply reset the PRAM to its default state. This will cause some data to be lost, specifically the date, the time, and the startup volume selection. Luckily, you can easily correct these settings using your Mac's System Preferences.
  1 Shut down your Mac.
  2
  3 Turn your Mac back on.
  4
  5 Immediately press and hold the following keys: command+option+P+R. That's four keys: the command key, the option key, the letter P, and the letter R. You must press and hold these four keys before you see the gray screen during the startup process.
  6
  7 Continue to hold down the four keys. This is a long process, during which your Mac will restart on its own.
  8
  9 Finally, when you hear the second startup chime, you can release the keys.
  10
  11 Your Mac will finish the startup process.
Once your Mac finishes starting, you can use the System Preferences to set the time zone, set the date and time, select the startup volume, and configure any display options you wish to use.
To do this, click the System Preferences icon in the Dock. In the System section of the System Preferences window, click the Date & Time icon to set the time zone, date, and time, and click the Startup Disk icon to select a startup disk. To configure display options, click the Displays icon in the Hardware section of the System Preferences window.
Still having problems? Try resetting the SMC or running the Apple Hardware Test
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