frankly, we need code samples from you. i haven't a clue what vBulletin is (/me smells a pre-made), but you should have no problem whatsoever establishing multiple connections to databases.

my %dbs;
$dbs{$sid_0} = DBI->connect("dbi::$driver0", $user0, $pass0) ||
  die "failed to establish connection to $sid_0 : $DBI::errstr\n";

$dbs{$sid_1} = DBI->connect("dbi::$driver", $user1, $pass1) ||
  die "failed to establish connection to $sid_1 : $DBI::errstr\n";
...
$sth_0 = $dbs{$sid_0}->prepare...
$sth_1 = $dbs{$sid_1}->prepare...
[download]

ad nauseum.

obviously using a hash is arbitrary; it just makes it easy to track your connections by some meaningful name.