[ame=http://www.youtube.com/watch?v=JwqiFO4JRgo]YouTube - How To Fix Error 100 In Mac App Store - iOS Vlog 251[/ame]
The Mac App Store was released today and it had some bugs. You're unable to purchase apps unless you download a free app the first time. This is because you need to agree to the terms and agreements, for some reason the paid ones get an error. This is the fix, hope it helps.
