Weird mouse issue with OS X 10.7.4 on 21" iMac I'm having some strange problems with my year-old iMac running OS X 10.7.4.
After clicking on a menu item on the top menu bar, the drop down menu that appears disappears instantly. This also happens when right clicking on the desktop or on an application in the dock. It's as if single clicks are getting counted as double clicks. 

Sometimes, the cursor just disappears. It reappears when moving the mouse, but keeps flickering.

It's not a problem with my Apple wireless mouse. I also tried a wired Logitech mouse and had the same problem; so, it must be a software bug, not a hardware problem.

I started experiencing the issue after doing a software update to OS X 10.7.4, but I'm not sure if this is the cause of the problem.

I have uploaded a video of the problem here: http://tinypic.com/r/2vxk9af/6
I've occasionally had problems over the years with weird mouse issues, and bar once, they were all fixed by deleting the "com.apple.driver.AppleHIDMouse" file located in ~user\Library\Preferences. Upon reboot the file will be recreated, and you can bak it up first in case it changes something. Software updates can sometimes change/corrupt plist files, and deleting them to fix issues is fairly common.

Worth a try if you're struggling for a fix.