Q: Unexplained behaviour or the trackpad.

Is there a Bluetooth device nearby with failing batteries?

If that is not the case, you have to take the computer to the nearby Apple store

to have the Trackpad checked out.

Best.

There are several possible causes for this issue. Take each of the following steps that you haven't already tried until it's resolved. Some may not be applicable.

1. Follow the instructions in this support article, and also this one, if applicable.

2. Open the Bluetooth preference pane in System Preferences and check for unknown or forgotten input devices. Disconnect any USB input devices that you aren't using.

3. Boot in safe mode and test, preferably without launching any third-party applications. If you don't have the problem in safe mode, but it comes back when you reboot as usual, stop here and post your results. If you can't boot in safe mode, do the same. If you booted in safe mode and there was no change, go on to the next step.

4. Reset the System Management Controller.

5. If you're using a Bluetooth trackpad, investigate potential sources of interference, including USB 3 devices.

6. A swollen battery in a MacBook Pro or Air can impinge on the trackpad from below and cause erratic behavior. If you have trouble clicking the trackpad, this is likely the reason. The battery must be replaced without delay.

7. Press down all four corners of the trackpad at once and release. If there's any effect, it's likely to be temporary, and the unit needs to be serviced or replaced.

8. There's a report that a (possibly defective) Thunderbolt Ethernet adapter can cause the built-in trackpad of a MacBook to  behave erratically. If you're using such an adapter, disconnect it and test.

9. There's also a report of erratic cursor movements caused by an external display that was connected but not turned on.

10. If none of the above applies, or if you have another reason to think that your computer is being remotely controlled, remove it from the network by turning off Wi-Fi (or your Wi-Fi access point), disconnecting from a Bluetooth network link, and unplugging the Ethernet cable or USB modem, whichever is applicable. If the cursor movements stop at once, you should suspect an intrusion.

11. Make a "Genius" appointment at an Apple Store to have the machine and/or external trackpad tested.

I had the same problem, simultaneously on a 2012 MacBook Air, and a MacBook from late 2008 (alu case).

In my case the issue was related to a third-party power source - as hinted at the bottom of this suport article http://support.apple.com/kb/TS1449 - which I picked up from Linc Davis' answer in this thread (THANKS LINC!) The moment I unplug that single culprit, BOTH track pads behave normally.

I want to enphasize: a SINGLE non-Appple power source was affecting BOTH notebooks connected to the same power socket, but naturally each with its own "brick": the MBAir with its original one, the MB2008 with the alternative. Something about the electronics of this crappy accessory creates back-currents or magentic fields in the entire power circuit from the wall socket onwards - as hinted by Apple. 

Hope this helps you, too!

Fred

My trackpad seems to be continually clicking randomly and it also moves around on its own. However once I put my MacBook Pro into safe mode the mouse was working properly. After I took safe mode off the mouse went back to having a mind of its own. Any idea?

Very odd multiple people start having bluetooth tracking problems right after the new year starts.  Just seems too weird to me.

I've had similar things happen now and again on all my devices that use a trackpad and found more often than not that I inadvertantly had something resting on the keyboard:)

If you've had your MacBook form 3-5 years, the swolled battery Linc mentioned could be the likely cause. I got mine in 2009 and had the problems you're describing. They seemed random and control of the cursor was a big issue. I took it into the Genius Bar and they told me it is likely a swolled battery. I had it replaced and picked it up 2 days later and the trackpad was back to normal.

I have had my desktop iMac with this external Tracpad for about a year now.  A few months ago the tracpad started acting erratically as if it was possessed.  I moved it aside and held my hands in the air completely away from it and it was selecting stuff and moving stuff all over the place.  The kids got a good laugh out of it.  Anyway, I found if I disconnected it and then reconnected it it would work fine for a while and then it would happen again.  I have been stumbling along that way for a few months and finally I have switched back to a mouse.  But the mouse is frustrating.  I was going to go buy a new tracpad but then I did some research read these posts and other threads and don't have confidence that a new one will be any better.  I tried the Apple Safe Mode thing and so far so good but you really never know when it will start acting up.  It is very intermittent.

Me again, no sooner had I posted this last post before the tracpad started freaking out again. I am in Safemode and it is still psycho.  This is not someone trying to control my computer.  You can tell that it is just random actions - like it is possessed.  I'm guessing there must be some sort of interference going on but I'm looking around my desk and don't spot anything new that I've added since I bought the computer and these problems did not occur until about 8 months into owning the tracpad.  I think there must be some sort of failure inside the device that makes it more sensitive to interference.  Wish Apple would research this.

I´m experiencing the same issue as blueandgold. The cursor is getting crazy, moving all over the place and random clicking. The trackpad isnt responding 99% of the time. I was able to control the macbook with a usb bluetooth mouse but now its nearly impossible to work with this as the mouse start clicking anywhere and even swaping desktops.

Its a Macbook Pro Retina (2012).

I don´t know what might be doing this. Nobody is moving the cursor as I managed to disconnect from wifi and the thing kept going.

This started happening when I connected the new mouse, but not sure if that the reason. I disconnected it, powered off and still happending. I also resetted the SMC, nothing happened. This also keeps going in safe mode.

I tryied everything, bluetooth, disabling, enabling.

The battery seems fine, it charges normally, so I don´t think its bothering the capacitive sensor from the trackpad.

I live in Argentina, so Apple Store isn´t available here. Really don´t know what to do at this point.

Hi masize. If you live in Argentina you are probably using a plug adapter of some sort which are generally unshielded. Try your Mac unplugged and the problem might disappear. (I had a similar problem)

Also, you do have plenty of official dealers and authorized service centers in Buenos Aires, listed in Apple's and other websites. I had great service and they do recognize apple's global warranty if applicable. Go have it checked!