This is a slightly more advanced problem than most of the ones I’ve covered so far, but this saved me so much time and aggravation, I wanted to share how I dealt with this problem in detail.
On OS X, Spaces and text expansion software don’t really play nicely. If you switch back and forth too quickly between spaces while you’re using text expansion (and certain other types of quick-text-input) software, the space can become stuck.
You’ll see this little guy, the Space changed indicator:
but although it normally disappears after about half a second, when this problem occurs it sticks to the screen and won’t go away. You can still use your mouse, but your keyboard locks up and you are unable to type anything. This happens with both built-in laptop keyboards and external keyboards you can use with laptops or desktops.
Until I did some serious digging into help threads, I was restarting my computer every single time this happened, which was incredibly annoying. But what I found after many suggestions and a fair amount of trial and error was surprisingly simple, if a little obscure.
The secret to un-sticking the Space changed indicator is a little weird: Using Exposé to turn off your screen for a second. Go to Settings > Exposé and Spaces, and select the Exposé side:
As you can see, I’ve already gone ahead and set the top left hot corner for my screen to “Put display to sleep.” If you click on any one of those corners, you’ll get this drop-down menu:
Once you’ve activated this hot corner, all you have to do is move your mouse into whichever corner you’ve selected, let the display go to sleep for a second or two, then wake it back up by tapping your keyboard or moving your mouse.
This is a trick that’s worked for me about 98% of the time to unlock everything. Every once in a while I have to go back to my previous technique of restarting the computer entirely, but that’s been a massive improvement over having to restart it every single time this happened.