error while updating ports: x11/xorg-libraries

[Huub]

Hi,

After a quite some time of not using the machine, I decided to update a 
PentiumIII pc running FreeBSD 6.2. Starting with "portupgrade -R 
firefox" it ends with:

[Updating the pkgdb <format:bdb_btree> in /var/db/pkg ... - 685 packages 
found (-0 +1) . done]
--->  Skipping 'graphics/cairo' (cairo-1.4.10) because a requisite 
package 'xorg-libraries-7.2_1' (x11/xorg-libraries) failed (specify -k 
to force)
--->  Skipping 'x11-toolkits/pango' (pango-1.16.5) because a requisite 
package 'cairo-1.4.10' (graphics/cairo) failed (specify -k to force)
--->  Skipping 'x11-toolkits/gtk20' (gtk-2.10.14) because a requisite 
package 'pango-1.16.5' (x11-toolkits/pango) failed (specify -k to force)
--->  Skipping 'www/firefox' (firefox-2.0.0.6,1) because a requisite 
package 'pango-1.16.5' (x11-toolkits/pango) failed (specify -k to force)
** Listing the failed packages (*:skipped / !:failed)
         ! x11/xorg-libraries (xorg-libraries-7.2_1)     (unknown build 
error)
         * graphics/cairo (cairo-1.4.10)
         * x11-toolkits/pango (pango-1.16.5)
         * x11-toolkits/gtk20 (gtk-2.10.14)
         * www/firefox (firefox-2.0.0.6,1)
--->  Packages processed: 34 done, 61 ignored, 4 skipped and 1 failed

So, starting to look for information about xorg-libraries, I've searched 
  in /usr/ports/CHANGES, MOVED and UPDATING but found nothing. Can 
someone please tell me how to get on with this?

Thank you.