Troubleshooting and Common Solutions 
Over the course of time there may be problems with your software. Proper maintanence and upgrades will help minimize these but they can still occur. This section of the manual will outline the most common problems that can occur and give the solution or workaround for them to get your site back up and running.

Solutions to Common Problems
When viewing my board, I get an error that says "Cannot add cookie information, headers already sent"
The most common reason for this is a blank or exta line in your config.php. You are not allowed to have anything outside the <?php and ?> delimiters. Not even a space. It is recommended to eliminate all extra lines and spaces before or after these delimiters.

I installed a new plugin and now my forum doesn't work. I can't login into the Admin Control Panel to fix this.
To temporarily disable the plugin system, edit config.php and add this line right under <?php
define('DISABLE_HOOKS'true); 
This will allow your forum to work and you can then login and delete the plugin via the plugin manager.

I have several domains pointed to my forums. However when users login via one domain, they get an error that says "In order to accept POST request originating from this domain, the admin must add this domain to the whitelist".
That error can happen when you post to a vBulletin form from an external referrer that isn't on the white list:

Admin CP -> vBulletin Options -> General Settings -> Post Referrer Whitelist


Edit this list to include all referrers that you use.

I have tried the above but cannot log into my Admin Control Panel to make the changes.
You can temporarily disable the Whitelist by editing your config.php file. Open this file in wordpad and in a line above the ?> add the following code:
define('SKIP_REFERRER_CHECK',true); 
When viewing my board, it has an error that says "There has been a slight problem with the database."
Please view the source of the page and compare the error to those listed in the section on troubleshooting MySQL. If the error isn't listed there, please open a support ticket at https://www.vbulletin.com/go/techsupport/
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