In Lion, if I keep pressing a key, why doesn't it repeat? I don't know if there are any settings to toggle, but I figured out that if I keep pressing a button on my keyboard it doesn't repeat it and displays only one character! Can this be fixed to go back to the previous repeating behavior?
This is a new "feature" that Apple introduced in Lion.  To disable no key repeat, enter 

defaults write -g ApplePressAndHoldEnabled -bool false

in Terminal, and then restart your computer.

Source: https://discussions.apple.com/message/15678809