PORTS: What is "Makefile broken" ?

[Payam]

Hi. I'm running FreeBSD 4.9.

Whenever I do a "cvsup ports-supfile" followed by a "portupgrade -a" 
some ports fail (Makefile broken, install error, unknown error) and then 
some of their dependants aren't built because of it.

Here is an example of a "Makefile broken"
=====================
angela root # cd /usr/ports/graphics/libexif
angela libexif # make
"/usr/ports/Mk/bsd.port.mk", line 2028: warning: String comparison 
operator should be either == or !=
"/usr/ports/Mk/bsd.port.mk", line 2028: Malformed conditional 
(${PKGINSTALLVER} < 20030417)
"/usr/ports/Mk/bsd.port.mk", line 2028: Need an operator
"/usr/ports/Mk/bsd.port.mk", line 4982: if-less endif
"/usr/ports/Mk/bsd.port.mk", line 4982: Need an operator
make: fatal errors encountered -- cannot continue
angela libexif #
=====================

There is apparently a problem with the Mk/bsd.port.mk file !!

Is there something I'm missing here? This happens with a lot of ports.

And then there are the "install error" and "unknown error" ports that I 
don't know what to do with either.

Any insights would be very much appreciated.

-Payam