Package version problem with portupgrade(1)

[Mark Ovens]

FreeBSD postie 4.9-RELEASE FreeBSD 4.9-RELEASE #1:
Sun Mar 21 19:46:39 GMT 2004
      root at postie:/usr/obj/usr/src/sys/POSTIE  i386

I'm trying to upgrade cups-base on this system, using packages (as the 
machine doesn't really have enough grunt for building ports), with 
portupgrade, but it is trying to get the wrong version:

postie# portupgrade -RPPv cups-base
--->  Session started at: Wed, 01 Sep 2004 17:27:46 +0100
--->  Checking the availability of the latest package of 'graphics/png'
--->  Fetching the package(s) for 'png-1.2.5_8' (graphics/png)
--->  Fetching png-1.2.5_8
++ Will try the following sites in the order named:
         ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/i386/packages-4.9-release/
--->  Invoking a command: /usr/bin/fetch -o '/var/tmp/png-1.2.5_8.tgz' 
'ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/i386/packages-4.9-release/All/png-1.2.5_8.tgz'
fetch: 
ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/i386/packages-4.9-release/All/png-1.2.5_8.tgz: 
File unavailable (e.g., file not found, no access)
** The command returned a non-zero exit status: 1
** Failed to fetch 
ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/i386/packages-4.9-release/All/png-1.2.5_8.tgz

The actual file in ports/i386/packages-4.9-release/All/ is png-1.2.5_2

I'm guessing that this is caused because my ports tree was cvsup'd and 
so is more up to date than the packages built for 4.9-RELEASE. Thing is, 
how to deal with it? I could set $PKG_SITES in pkgtools.conf to use 
packages-4.9-release/Latest but the files there have no version number 
at all, e.g. png.tgz

What's the best solution here - before I go and screw my system ;-)

Thanks.

Regards,

Mark