Comment 4 for bug 317366

Menu is broken for me as well.

Effects: X11 hangs except for the mouse until the
urxvt in question is killed from a console; a grab maybe?

work around is disabling popups in .Xdefaults
(use xrdb -merge ~/.Xdefaults if necessary):

(if you still want perl running)
Rxvt.perl-ext-common: defaults,-option-popup,-selection-popup
otherwise its:
Rxvt.perl-ext:
Rxvt.perl-ext-common:

likely culprits are:
/usr/lib/urxvt/urxvt.pm # contains code for popups
/usr/lib/urxvt/perl/option-popup # menu itself
/usr/lib/urxvt/perl/selection-popup # possibly innocent??