[Libreoffice] FOO_GTK error when running autogen.sh

OK, folks, I've got another issue, this time when running autogen.sh.

Here's the command I'm running (OS is CentOS 5).

./autogen.sh --with-git --with-num-cpus=3 --without-junit --disable-kde4

I get the following configure error:

checking for autoconf... yes
checking for flex... yes
checking for bison... yes
checking for ccache... no
checking for distcc... no
checking for widget sets... checking for FOO_GTK... no
configure: error: Gtk+ library requirements were not met

If I throw the "--disable-gtk" switch, autogen.sh is happy.  I checked, 
and I'm seeing the gtk+-devel and gtk2-devel packages installed.
BTW, this is a new box, a 64-bit Core 2 Duo running 64-bit CentOS 5.  
Both the 32- and 64-bit versions of the gtk+ and gtk2 binaries and 
"-devel" packages appear to be installed.  I made sure by yum 
install'ing these packages, and they're showing up as already installed.

Suggestions?

--TP