I was having major problems with Spaces today, and I didn't want to reboot my machine because I had a ton of tabs open in Safari. Spaces would not respond to Command-Tab or switching apps with the Dock. I was only able to activate Spaces with my hot key. I looked through the processes, and there was nothing whose name contained spaces. I turned off Spaces in System Preferences and turned it back on. That didn't help either. I even ran the Spaces.app, but there is no way to force quit it. SO I went out on a limb and tried an old reliable method for fixing Mac window weirdness: I killed the Dock's process, causing it to restart. Viola! Spaces works fine now. Apparently Spaces is merely a new feature of the OS X Dock. So if you find yourself in this situation, here's what to do: Launch Terminal, in Applications » Utilities. Type killall Dock...

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