its not to hard to get your keyboard settings screwed up when changing them around. in the settings editor there are several places that you can view modify the keyboard control window manager, window manager tweaks and keyboard are a few places to check. maybe setting everything back to default values and then searching in those lists for the crashy keystroke .
http://docs.xfce.org/xfce/xfwm4/wmtweaks
is there a way for me to use give puredata exclusive response to the keyboard regardless if i click on another window and bring it into focus with the mouse?
also is there a way to use 2 keyboards and have one of them as dedicated input to a specific puredata window. maybe by re piping the kb signal directly to the window?