If upgrading MediaWiki to a version that supports postgres 8.3, another option could be to export from the old db as XML (using the Special:Export page) then import once the new wiki's installed with a blank database - that's what I'm going to try, I've had problems upgrading MediaWiki databases in the past, possibly due to customised installations. This should hopefully render any database issues irrelevant.
You need to know the names of the pages to export, but could get those with a simple query direct to the database like
SELECT pagetitlecolumn FROM tablewherepagetitlesarestored;
