Portupgrade fails to upgrade after using portsnap

[Jez Hancock]

Hi all,

For a long time I've been using cvsup and portupgrade to update the ports
tree once a week; this has worked well for years now.  Recently though I
changed to using portsnap to update the ports tree, still using portupgrade
once a week to update the ports.  I followed the method outlined in the
handbook more or less for upgrading using portsnap, essentially running a
cronjob:

portsnap cron && portsnap update && portupgrade -arRF && pkg_version -v -I
-l "<"

to grab and extract the latest port snapshot, fetch any newer port
distfiles/tarballs and then report by mail what ports are out of date.

This worked well for a few weeks up until Feb 25th - since then not a single
out of date port has been reported and 'portupgrade -arR' fails to upgrade
anything. I thought this might have been to do with the recent ports freeze,
though checking now I see that only went on from the start of March...

I've changed back to use cvsup and the old method - basically 'cvsup -g -L2
supfile && cd /usr/ports && make fetchindex && portsdb -u' - but still no
joy.  I was convinced it was the ports db files that were out of synch and
thought this might do the trick to fix the problem, but unfortunately no -
if I view the resulting INDEX file from this procedure I can see there are
ports out of date as well, it's just 'portupgrade -arR' etc refuses to find
any updates.

Questions then:

What could the problem be?
For future reference what is the best way to purge the ports system of out
of date db files and regenerate them all so 'portupgrade -arRi' will work?

Cheers.
--
Jez Hancock