Let's set the scene: It's Monday morning, and you've been working tirelessly all weekend, tweaking and putting finishing touches on a big Keynote presentation that you'll be using at today's board meeting. Now that it's finished, you decide to run through it one last time, just to be safe. So you fire up Keynote, and your heart sinks as you stare unbelieving at the message above.
"WHAT?! I just opened it this morning! What do you mean it's not valid?" You're practically screaming at your computer now, and repeatedly trying to open the file to no avail. After taking a few moments to calm down and avoid tossing your Mac out the window, you suddenly remember the Versions feature in Lion that automatically saves version
