A problem which has been bugging me for a while is my Konsole and Yakuake terminal sessions ceasing to respond to input for no apparent reason. The symptoms are always the same: the session seemingly stops responding to key presses, yet if I was running screen inside the session, reattaching it elsewhere reveals the characters from the missing key presses.
The answer turns out to be that hitting scroll lock locks the terminal so that the arrow keys scroll it rather than cycling through previous commands, and this also prevents key presses updating the display. My Yakuake hotkey is F12, which is next to scroll lock on my laptop.
So now you know.