xorg-x11 isn't in the updates directory.  The following two packages are:
- xorg-x11-libs 
 - xorg-x11-Mesa-libGL
 
Which when you execute the following you see:
# rpm -e --test xorg-x11-libs xorg-x11-Mesa-libGL
error: Failed dependencies:
        libICE.so.6 is needed by (installed) libungif-4.1.3-1.el4.2.i386
        libICE.so.6 is needed by (installed) libungif-progs-4.1.3-1.el4.2.i386
        libICE.so.6 is needed by (installed) gifsicle-1.48-1.el4.rf.i386
        libSM.so.6 is needed by (installed) libungif-4.1.3-1.el4.2.i386
        libSM.so.6 is needed by (installed) libungif-progs-4.1.3-1.el4.2.i386
        libSM.so.6 is needed by (installed) gifsicle-1.48-1.el4.rf.i386
        libX11.so.6 is needed by (installed) libungif-4.1.3-1.el4.2.i386
        libX11.so.6 is needed by (installed) libungif-progs-4.1.3-1.el4.2.i386
        libX11.so.6 is needed by (installed) gifsicle-1.48-1.el4.rf.i386
This tells you that these packages are required by gifsicle and linungif.  Both of which are part of the OCR spamassassin plugin.