Please mask virtual/postgresql-base-8.3 along with =dev-db/libpq-8.3* and =dev-db/postgresql-8.3*. Otherwise some packet managers (paludis) complains about masked dependencies.
Thanks for the report, assigning to maintainers
We don't want to block the virtual though, as you can still install if from other means.
I've removed the offending ebuilds from portage and have removed the mask. That should fix this issue.