Q: Unusable Trackpad or the crazy pointer! :-(

I've experienced similar issues when by accident I touch the trackpad with a wet finger, or something, obviously not wet that I can damage it, but it gets crazy, and when you move it, it stays in the same place and moves just a bit.

How I fixed it was rebooting my Macbook Pro (mid 2012), and it absolutely fixed. Never experienced it again.

I can definetely say it's Software if you say that connecting an external mouse to the Macbook Pro still doesn't move the pointer.

What you could try doing and would definetly would solve it, is reinstalling OSX. To do this, it's quite simple.

1) Power off your Mac.

2) Turn it on, and once you see the white screen hold the Option Key (ALT) until you see that 2 big images of hard drives appear. You'll see one as your main drive, and the other as Recovery.

3) Go ahead and click on recovery.

4) Select Disk Utility in the menu.

5) Erase the Main HD / SSD (Formatting).

6) Once done this, go back to the menu and click Reinstall OSX.

7) Follow what it says.

Hope this helped you!

Later.

There are several possible causes for this issue. Take each of the following steps until it's resolved.

1. Follow the instructions in this support article.

2. Reset the System Management Controller.

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

4. 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.

5. 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.

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

7. If none of the above applies, or if you have another reason to think 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.

8. Make a "Genius" appointment at an Apple Store to have the machine tested.

I got the same problem today, and things got really uncontrollable. I updated to the latest ML 10.8.4 and I wonder if it had anything to do with this problem.

Only restarting the laptop temporarily fixed the issue, but after a while, without even touching the trackpad, the mouse started behaving like a fly jumping around.

I tried fixing the permissions but it didn't work.

A friend suggested to turn off the internet in case the computer could be hacked, and surprisingly, that stopped it. Problem is that I need to use internet to work, so what are suggestions to try?

I made a Genius appointment so I hope this can be fixed tomorrow, but my laptop is out of warranty and I really would like to avoid replacing the trackpad.

Any help sharing fixed stories would be appreciated.

Chiming in with same problem here.....sounds like it's an Apple problem and hopefully they fix it soon at $70.00 a trackpad

Update: I tried all the suggestions provided by Linc without success. I ended up at the Genius bar, they tested the trackpad, and even when it passed the test, there were a few spots that didn't work properly so I had it replaced. After $90, and two days of using the laptop, I haven't had any more problems!