missing key: categories: Cannot read the portsdb!
/usr/local/lib/ruby/site_ruby/1.8/portsdb.rb:567:in `open_db': database file error (PortsDB::DBError)
from /usr/local/lib/ruby/site_ruby/1.8/portsdb.rb:736:in `port'
from /usr/local/lib/ruby/site_ruby/1.8/portsdb.rb:924:in `all_depends_list'
from /usr/local/lib/ruby/site_ruby/1.8/pkgdb.rb:915:in `tsort_build'
from /usr/local/lib/ruby/site_ruby/1.8/pkgdb.rb:907:in `each'
from /usr/local/lib/ruby/site_ruby/1.8/pkgdb.rb:907:in `tsort_build'
from /usr/local/lib/ruby/site_ruby/1.8/pkgdb.rb:929:in `sort_build'
from /usr/local/lib/ruby/site_ruby/1.8/pkgdb.rb:933:in `sort_build!'
from /usr/local/sbin/portupgrade:694:in `main'
from /usr/local/lib/ruby/1.8/optparse.rb:755:in `initialize'
from /usr/local/sbin/portupgrade:210:in `new'
from /usr/local/sbin/portupgrade:210:in `main'
from /usr/local/sbin/portupgrade:1981


portupgrade -a 使用とすると上記のエラーが出ます。　何が悪いのかさえわからないです。
どなたか助けてください

FreeBSD6.2