I preformed a CVS update yesterday morning 09Feb2006 and attempted to build an updated firefox. After doing the regular port upgrade cycle of going and rebuilding the dependencies I came back to a bad build. Figuring that this was just an issue with fetching the sources and running out of time to delve further I checked again toady. Same error. The actual error message is 

root@# make
===>  Building for cairo-1.0.2_1
make  all-recursive
Making all in pixman
Making all in src
Making all in src
Making all in doc
Making all in public
Making all in test
/bin/sh /usr/ports/graphics/cairo/work/gnome-libtool --tag=CC --mode=link cc  -O2 -fno-strict-aliasing -pipe   -pthread -o imagediff  imagediff.o libcairotest.la ../src/libcairo.la  -pthread -lm
cc -O2 -fno-strict-aliasing -pipe -pthread -o .libs/imagediff imagediff.o -pthread  ./.libs/libcairotest.a ../src/.libs/libcairo.so -L/usr/X11R6/lib -lXrender -lX11 -lXext -L/usr/local/lib -lpng -lfontconfig -lfreetype -lz -pthread -lm -Wl,--rpath -Wl,/usr/local/lib
/usr/bin/ld: warning: libexpat.so.5, needed by /usr/X11R6/lib/libfontconfig.so, not found (try using -rpath or -rpath-link)
/usr/X11R6/lib/libfontconfig.so: undefined reference to `XML_SetElementHandler'
/usr/X11R6/lib/libfontconfig.so: undefined reference to `XML_SetDoctypeDeclHandler'
/usr/X11R6/lib/libfontconfig.so: undefined reference to `XML_ParserFree'
/usr/X11R6/lib/libfontconfig.so: undefined reference to `XML_SetCharacterDataHandler'
/usr/X11R6/lib/libfontconfig.so: undefined reference to `XML_ErrorString'
/usr/X11R6/lib/libfontconfig.so: undefined reference to `XML_ParseBuffer'
/usr/X11R6/lib/libfontconfig.so: undefined reference to `XML_ParserCreate'
/usr/X11R6/lib/libfontconfig.so: undefined reference to `XML_SetUserData'
/usr/X11R6/lib/libfontconfig.so: undefined reference to `XML_GetErrorCode'
/usr/X11R6/lib/libfontconfig.so: undefined reference to `XML_GetBuffer'
/usr/X11R6/lib/libfontconfig.so: undefined reference to `XML_GetCurrentLineNumber'
*** Error code 1

Stop in /usr/ports/graphics/cairo/work/cairo-1.0.2/test.
*** Error code 1

Stop in /usr/ports/graphics/cairo/work/cairo-1.0.2.
*** Error code 1

Stop in /usr/ports/graphics/cairo/work/cairo-1.0.2.
*** Error code 1

Stop in /usr/ports/graphics/cairo.
root@#

Fix: 

I am currently un aware of a fix for this but will work on it over the weekend.
How-To-Repeat: I ran a CVSup on my work test mail and web servers as well as my machines at home and all of them are stoping at this error. I would guess that this can be repeated byt trying to rebuild this port.