Having trouble with mixed table collations on a vbulletin database ? A mixture of collations like latin1_general_ci , latin1_spanish_ci, latin1_swedish_ci. For vbulletin to upgrade properly from a VB3 to VB4 it needs all tables to retain the same collation apparently.
This is great little script below ( which i lost the link where i got it from other wise i would post the link ) which allows you to enter the database info and the charset that you wish the tables to run in , you then upload the script to your server in a PHP file and navigate to the URL . It will then take some time to convert all the tables and returns a message if its successful .
mysql_query("ALTER TABLE $value COLLATE [B]utf8_general_ci[/B]");
echo "The collation of your database has been successfully changed!";
Another issue that you may come across especially on non english boards is invalid characters spread across the content, this can usually be solved by uploading the countries language packs which are listed here : vbulletin.com/forum/forumdisplay.php/96-vBulletin-Language-Packs