"RecursiveDependencyError" at all portinstall attempts on FreeBSD 8.1

[Ben DJ]

i've installed FreeBSD 8.1

 uname -a
  FreeBSD test.loc 8.1-RELEASE FreeBSD 8.1-RELEASE #0: Mon Jul 19
02:55:53 UTC 2010
root at almeida.cse.buffalo.edu:/usr/obj/usr/src/sys/GENERIC  i386

and, 'portupgrade',

 pkg_info | grep -i portupgrade
  portupgrade-2.4.6_4,2 FreeBSD ports/packages administration and
management tool s
 portupgrade --v#ersion
  portupgrade 2.4.6
 portinstall --version
  portinstall 2.4.6

but at portinstall of any/all pacakges (here, an e.g. with 'nano'), i
get a  "(RecursiveDependencyError)",

portinstall nano
[Gathering depends for editors/nano
....../usr/local/sbin/portinstall:856:in `get_all_depends': recursive
dependency (RecursiveDependencyError)
        from /usr/local/sbin/portinstall:879:in `get_all_depends'
        from /usr/local/lib/ruby/1.8/set.rb:195:in `each'
        from /usr/local/lib/ruby/1.8/set.rb:195:in `each_key'
        from /usr/local/lib/ruby/1.8/set.rb:195:in `each'
        from /usr/local/sbin/portinstall:878:in `get_all_depends'
        from /usr/local/sbin/portinstall:879:in `get_all_depends'
        from /usr/local/lib/ruby/1.8/set.rb:195:in `each'
        from /usr/local/lib/ruby/1.8/set.rb:195:in `each_key'
        from /usr/local/lib/ruby/1.8/set.rb:195:in `each'
        from /usr/local/sbin/portinstall:878:in `get_all_depends'
        from /usr/local/sbin/portinstall:879:in `get_all_depends'
        from /usr/local/lib/ruby/1.8/set.rb:195:in `each'
        from /usr/local/lib/ruby/1.8/set.rb:195:in `each_key'
        from /usr/local/lib/ruby/1.8/set.rb:195:in `each'
        from /usr/local/sbin/portinstall:878:in `get_all_depends'
        from /usr/local/sbin/portinstall:897:in `get_notinstalled_depends'
        from /usr/local/sbin/portinstall:777
        from /usr/local/sbin/portinstall:755:in `each'
        from /usr/local/sbin/portinstall:755
        from /usr/local/lib/ruby/1.8/optparse.rb:1310:in `call'
        from /usr/local/lib/ruby/1.8/optparse.rb:1310:in `parse_in_order'
        from /usr/local/lib/ruby/1.8/optparse.rb:1306:in `catch'
        from /usr/local/lib/ruby/1.8/optparse.rb:1306:in `parse_in_order'
        from /usr/local/lib/ruby/1.8/optparse.rb:1254:in `catch'
        from /usr/local/lib/ruby/1.8/optparse.rb:1254:in `parse_in_order'
        from /usr/local/lib/ruby/1.8/optparse.rb:1248:in `order!'
        from /usr/local/lib/ruby/1.8/optparse.rb:1241:in `order'
        from /usr/local/sbin/portinstall:565:in `main'
        from /usr/local/lib/ruby/1.8/optparse.rb:791:in `initialize'
        from /usr/local/sbin/portinstall:229:in `new'
        from /usr/local/sbin/portinstall:229:in `main'
        from /usr/local/sbin/portinstall:2213

i've uninstalled ruby & portupgrade, and reinstalled portupgrade, but no change.

any hints as to what to fix?

ben