A couple of days ago, I opened an image up in Preview only to find that the application would not respond to any clicks or keyboard shortcuts I made. If I were to hover over an icon on the top bar, it would recognize that I was doing that, but not do anything if I clicked on it. Ultimately, the only way to close the program to perform a force quit with Cmd-Opt-Shift-Esc or right-click on the dock and go to "Quit". It does not show up as not responding in the Force Quite menu, and the problem does not go away if I reboot the computer.
I've also experienced the problem in two other apps to date - the App Store and TextEdit. Both will act like they're perfectly okay until I actually go to click on something, in which case they won't respond at all. There's no spinning pinwheel or freezing - it just acts like nothing is happening. (For example, if I launch the App Store from my browser directly to an app page, the "Download" or "Purchase" button will highlight when you hover over it but cannot be pressed. I have launched it from Finder, as well, so it's not that contributing to it.)
These are the only apps I've noticed that are doing it, but they're all Apple apps. In contrast, Finder, iTunes, and Safari work as well as ever. Any help would be much appreciated.