Since 1.03 or something you should be getting one keydown, a whole bunch of keyrepeat's and a keyup message, are you on ubuntu gnome or something else? This may also be something that is broken in fltk, sorry I can't test right now.
To help debug try adding a
just after waitevent()
To help debug try adding a
debuglog currentevent.tostring()
just after waitevent()