problems compiling Abiword and almost any Gtk app to FreeBSD 6.2: fusefs-kmod

[pedro alves]

   Hello
   I am running FreeBSD 6.2-release on a Thinkpad600.
   I am trying to build a decent workstation for my work (text editing
   and minor plain web browsing).
   I do cvs updates weekly of the ports.
   However recently I found that I can't build abiword or gnumeric or any
   other gtk2 app, because I get the following an error compiling
   fusefs-kmod.
   ==> fusefs-kmod-0.3.9.p1.20080208_1 requires the userland sources to
   be installed. Set SRC_BASE if it not in /usr/src.
   Well I have source files installed
   (sysinstall->Distribution->source->sys & base.).
   However no change ... I get always the same error using MAKE INSTALL
   CLEAN or PORTINSTALL.
   Can some one provide an easy to understand method to sold this
   annoying problem.
   Thanks.
   PS: I am an newbie user of FreeBSD.