[kh99]

Originally Posted by squishi

You are probably right. I will add the trace to the plugin instead of the function.

Actually I think I was wrong. To call a member function it would have to use $this->fetch_userinfo, and the parameters are wrong, so it is calling the one in functions.php. I think you're right that the first time it's called $vbulletin->userinfo isn't set even though it's used at the start of that function. It could be that the "is not an array" error message doesn't appear because messages are turned off.

I don't know what your plugin does, but maybe you could use hook fetch_userinfo and check $user instead of $vbulletin->userinfo.