When I use the DEL key on the numeric keypad, to edit the property fields instead of deleting the character that I want to delete… it inserts invisible characters. When I look at the code generated I see squares.
I can reproduce this on all my machines. Windows XP, Windows 7 32 bit, Windows 7 64 bit. Just use the del key on the numeric key pad to delete characters in the property lists. You should notice that when using the del key in the keypad it does not delete characters. If you then save the project, and go look in the XDS file with a normal file editor, you should see bizare characters (squares) in the properties where you tried deleting characters.
I do have a swiss german keyboard... but I would imagine that the numeric keypad is the same for most type of keyboards.