A long time ago (over a year) I converted from phpBB to IPB. Everything went fine with the conversion and everything was working perfectly up until the last IPB update.
Now, all the old redirects (/forum/viewtopic.php?t=1234) go to a IPB 404 page.
I've looked at the redirect files and the databse and everything is still there and running the query manually returns the correct result.
$row = $DB->buildAndFetch( array( 'select' => 'ipb_id', 'from' => 'conv_link', 'where' => "foreign_id='".ipsRegistry::$request['t']."' AND type='topics' AND app='".$app['app_id']."'" ) );