The German keyboard driver for Windows defines several so-called "dead keys", which are used to enter accented characters. For example, the caret key '^' followed by the letter i yields î. If the dead key is followed as a space, the result is just the dead key. For example, to enter a real caret, we type the caret key, followed by a space.
J does not recognize this, and makes it impossible to enter those characters (in particular, the caret (^) and the back quote (`)) using the keyboard. If I type a caret, followed by a space, only the space is entered. It is purely a keyboard problem, since copy-and-paste from other applications work fine.
I'm using J 0.23.0
Unfortunately, I don't have a German keyboard on which to repro this. Can you recompile J with the Dispatcher.DEBUG_KEY_PRESSED flag set to true, type a few characters using the dead keys, and paste the DEBUG output found in your .j/log file into this bug?
Which JVM are you using and which version?