There seems to be a bug in MT 3.11's MT::PluginData that breaks MT::Blacklist if you use PostgreSQL. MT's authors are using an (what I call) flaw in MySQL that makes MySQL let you store binary data in an text field. They assume it's the same on PostgreSQL, but as PostgreSQL is more of a database then MySQL it won't.
Therefore it will break. On
MT::Blacklist's Forum there is a thread going on how to fix this. There is a link to
David Rayne's Weblog that hints how to fix this issue.
It consists out of editing lib/MT/PluginData.pm to have another data subroutine.