Current firefox trunk codes use xinerama by default, so the trunk build depends on libXinerama.so.
But that library is under /usr/X11/lib and no symbolic link under /usr/lib (e.g. /usr/lib/libXinerama.so --> /usr/X11/lib/libXinerama.so) points to it.
*** Test case ***
Verify that libXinerama.so & libXinerama.so.1 symlinks exist in both
/usr/lib and /usr/lib/64 pointing to the correct counterpart files in
/usr/X11/lib & /usr/X11/lib/64.
This problem also affects Nevada build 64. In this case both xscreensaver and xscreensaver-demo does not work. So the common user is not able to lock his screen.