Q: Trackpad Glitch -- dragging everything: problem is not keyboard or mouse

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, 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. 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.

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

9. 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.

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

I had a similar problem all of which developed after the upgrade that came with iOS7 with my external Apple trackpad. Trying to move the curosr was the first one. It moved erratically.

I thought I had solved the problem by turning off the trackpad, trashing the trackpad preferences, then restart and reconnecting the trackpad.

All was fine for a day, then yesterday, I couldn't just touch the pad to select. I solved that by opening preferences and unchecking and rechecking that feature.

This Am I got up and lo and behold, when I tried dragging a window with three fingers, I couldn't do it. I could click on the window and move it but three finger drag wanted to swipe everything over.

I fixed the problem again by opening the preferences and clicking the three finger feature off and back on.

I had the same issue this weekend, so I contacted the Apple Support through Chat. I performed some troubleshooting procedures the guy requested me to do but the problem continued. It was really frustrating. He recommended me to take it to a Genius Bar. I decided to disable temporarily the trackpad and connect an external mouse to be able to work. In any case I continued googling for more info about the issue and found that pressing the four corners of the trackpad worked in some cases so I did it and enabled the trackpad back. It totally solved it. At least it seems so. It worths a try.