Ports requiring X11 on Leopard

Hi, I have recently started using Leopard and have found that ports that require X11 cannot find the necessary libraries. This is frustrating as they worked fine on Tiger. I was able to solve my problems by adding configure.pkg_config_path ${prefix}/lib/pkgconfig:${x11prefix}/lib/pkgconfig the Portfile . Why is this not necessary on Tiger? I don't remember configuring anything special when I set up Tiger. Also, which is better to use: lib:libX11:XFree86 or port:xorg-libX11 ? Michael