While working in IntelliJ IDEA, the keyboard occasionally locks in a way that delete or < > ^ keys don't work properly anymore, in a way that delete doesn't do anything anymore, and the arrow keys scroll the entire source code / editor section.
I don't know if I am accidentially some kind of shortcut, but the only way I can get it back to normal again is closing and re-opening the IDE, which is annoying of course.
I'm on Mac OS X Lion, latest IntelliJ IDEA CE (11.1.1), but also had it before with the previous versions.
This answer on superuser.com worked for me:
ibus-daemon -rd