On vbulletin, if there's an DB error if you View the page source it will show you the error (something like this): <!--
Database error in vBulletin :
Invalid SQL:
SELECT *
FROM datastore
WHERE title IN ('','options','bitfields','attachmentcache','forumcache','usergroupcache','stylecache','languagecache','products','pluginlist','cron','profilefield','loadcache','noticecache','userstats','birthdaycache','maxloggedin','iconcache','eventcache','mailqueue','blogstats','blogcategorycache');
MySQL Error : Table 'vbulletin.datastore' doesn't exist
Error Number : 1146
Request Date : Sunday, July 13th 2008 @ 11:36:04 AM
Error Date : Sunday, July 13th 2008 @ 11:36:04 AM
Script : http://xxx
Referrer : http://xxx
IP Address : xxx.xxx.xxx
Username :
Classname : vB_Database
MySQL Version :
-->