Last night while performing routine computer/internet tasks, my computer suddenly decided to repeatedly receive SPACE input. My computer is a laptop, but I've got it hooked up to an HD monitor & I'm using a wireless bluetooth keyboard & a pen tablet. So, the first thing I check is that the spacebar isn't stuck on either keyboard. They weren't. Then I turned the bluetooth keyboard so that only the laptop's built in keyboard would be active. Nope, still actively spacing. Then, frustrated, I looked to see if there's some form of 'sticky keys' combination for the space bar. There wasn't, and why should there be? Utterly perplexed, I do the only thing I can think of & turn the whole computer off. Which, by the way, is incredibly difficult if the space bar is being held down. Try it some time.
That seemed to work this morning when I decided to log back on. 3 hours later, it's at it again! WTH? All the web site I'm viewing are scrolling to the bottom, all my dialog boxes are being closed as soon as they open, and all of my google searches look like https://www.google.com/search?q=++++++++++++++++++++++++s++++++p+++a+++c++e++++++++b++a++r+++++++++++s++++++t++++u++++c++k+++++++&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a.
About that time, I remembered that I had plugged in my backup keyboard: a 2-year old Logitech wave wireless keyboard/mouse combo. I looked down at the floor where it was sitting to see that the space bar was being pressed down by my shoe. I promptly unplugged it. Problem solved.
Smart moment there.