--- a/src/de/uapcore/sudoku/SudokuTextField.java Sat Jan 26 19:34:31 2013 +0100 +++ b/src/de/uapcore/sudoku/SudokuTextField.java Sun Jan 27 15:03:57 2013 +0100 @@ -59,10 +59,12 @@ private void handle(KeyEvent e) { char c = e.getKeyChar(); if (!e.isAltDown() && !e.isControlDown() && - Character.isLetterOrDigit(c)) { + !Character.isISOControl(c)) { // Perform clean input check if (getText().length() > 0 && getSelectedText() == null) { - e.consume(); + if (c != KeyEvent.CHAR_UNDEFINED) { + e.consume(); + } } else { if (c < '1' || c > '9') { e.consume();