what is this error?

[Chad]

Fatal error: Cannot use object of type vB_Session as array in /home/chadi/public_html/showthread.php(1912) : eval()'d code on line 33

Using php 5.14 / mysql 4.1 with vb3.5.4

[Lats]

You've made a template change in showthread?

[Floris]

3.5.4 is an outdated version. I recommend to upgrade to 3.5.5 - if not only to fix the reported security issue.

That said, are you running any plugins?

[Steve Machol]

This error is from a plugin you've installed. You need to disable each of your plugins then turn one at a time to see which one is causing this.

If you cannot log into the Admin CP then to disable the plugin system, edit config.php and add this line right under <?php

define('DISABLE_HOOKS', true);

This will disable all hooks and allow you to log in properly with no hooks running.

http://www.vbulletin.com/docs/html/disable_plugins