When you get the error, view the page source for that page and you will see the actual database error near the bottom of that page. It will have some information like this:
Code:
The actual mysql query/code/problem....
MySQL Error : some sort of something here
Error Number : another something here
Date : Sunday, April 13th 2008 @ 11:16:43 AM
Script : http://address.path.path/page.php
Referrer :
IP Address : **.***.**.***
Username : username
Classname : database
If it does not show there (and the recent versions of vb4.x do not show it there), then you will need to get the database error from the email that you get sent when you have database errors on your site.