kdelibs3 configure script reports LibXext error

[OleVoß]

I'm trying to install the KDE3 which came with freeBSD 4.9 from ports.
Unfortunately the installation fails while installing the kdelibs3 with the 
following error:


---------------------------------
checking for libXext... no
configure: error: We need a working libXext to proceed. Since configure
can't find it itself, we stop here assuming that make wouldn't find
them either.
===>  Script "configure" failed unexpectedly.
Please report the problem to kde at FreeBSD.org [maintainer] and attach the
"/usr/ports/x11/kdelibs3/work/kdelibs-3.2.0/config.log" including the output
of the failure of your make command. Also, it might be a good idea to provide
an overview of all packages installed on your system (e.g. an `ls
/var/db/pkg`).
*** Error code 1

Stop in /usr/ports/x11/kdelibs3.
---------------------------------

But LibXext IS installed and 'ldconfig -r' does list it. What am I doing wrong?

Thanks,

Ole.