The -safe-mode flag definitely does neutralize the bug, for some reason.
This isn't an rc issue or anything, bug shows up on a freshly installed and completely vanilla Conkeror.
Possibly irrelevant details about my system:
Debian Testing (Wheezy)
Mozilla XULRunner 8.0 - 20111109093931
xorg 1:7.6+9
xmonad 0.9.2 |