Can you press certain keys on your computer?

Ok. I place a computer, and I type a program to run, let's say "adventure". I go press enter to run it, and it does nothing. I've had errors like this before, like when no "a" popped up when I pressed "a". It's not just the key, as I am able to type with it in normal Minecraft Chat. Have any of you experienced this error?

Split into new topic.

Sometimes when you alt-tab into Minecraft with the computer open, the keyboard doesn't work until you click the screen.