sigc not sending 'c'

[Bruce Sherwood <Bruce_Sherwood ncsu edu>]

On two different laptops running Ubuntu and using sigc 2.0, I have the 
bizarre situation that all keypresses generate events except lower-case 
'c' (shift-c does generate an event, as do alt-c, ctrl-c, and 
ctrl-alt-c). Here is the connect statement (and the keypress handler 
returns true):

area->signal_key_press_event().connect(
        sigc::mem_fun( *this, &display::on_key_pressed));

Though I couldn't find any documentation on an optional second argument, 
I did find a note from someone who added a second argument, "false", as 
shown below (and then returned true from the keypress handler, 
supposedly to alert sigc not to do any more processing):

area->signal_key_press_event().connect(
        sigc::mem_fun( *this, &display::on_key_pressed), false);

I haven't a clue what to try to fix the problem. Any ideas?

Bruce Sherwood