portupgrade problems

[Andrea Venturoli]

Hello, I have a strange problem on a couple of FreeBSD 4.7 machines which share the same port tree (via NFS).

Whenever I try to upgrade a port I get:

/usr/local/lib/ruby/site_ruby/1.6/pkgdb.rb:310:in `deorigin': failed to convert nil into String (PkgDB::DBError)
        from /usr/local/lib/ruby/site_ruby/1.6/pkgdb.rb:903:in `tsort_build'
        from /usr/local/lib/ruby/site_ruby/1.6/pkgdb.rb:902:in `each'
        from /usr/local/lib/ruby/site_ruby/1.6/pkgdb.rb:902:in `tsort_build'
        from /usr/local/lib/ruby/site_ruby/1.6/pkgdb.rb:894:in `each'
        from /usr/local/lib/ruby/site_ruby/1.6/pkgdb.rb:894:in `tsort_build'
        from /usr/local/lib/ruby/site_ruby/1.6/pkgdb.rb:916:in `sort_build'
        from /usr/local/lib/ruby/site_ruby/1.6/pkgdb.rb:920:in `sort_build!'
        from /usr/local/sbin/portupgrade:674:in `main'
        from /usr/local/sbin/portupgrade:207:in `initialize'
        from /usr/local/sbin/portupgrade:207:in `new'
        from /usr/local/sbin/portupgrade:207:in `main'
        from /usr/local/sbin/portupgrade:1834

Any hint?

 bye
        av.