[Mukashi]

Originally Posted by DragonByte Tech

Are you using a custom product manager? If so, please try disabling it.

I don't have 4.1.11 installed anywhere, please tell me the contents of that line.

In 4.1.11, that line is

$vbulletin->pluginlist = array_merge($vbulletin->pluginlist, $vbulletin->pluginlistadmin);

Which comes under the heading of

// enable any hooks -- this is mainly necessary for importing templates (template_safe_functions hook)

We're not using a custom product manager, just the standard one in vBulletin. We do have a heck of a lot of addons, though we've never had any compatibility issues before. I should note also that despite that error, the addon does appear to have installed correctly.