Well I can only tell you what users have posted here about
vbSEO and there solution to there issue.
Our code to support vb4 is really simply as all we do is check the vbulletin simply_version to grab the
vb version and then load the appropriate
vb stuff based on whether your using vb3 or vb4.
If you turn off
vbseo you can see things work fine
Now the one thing I see on your site is your bburl setting in vbulletin appears to be empty or
vbseo is blocking that variable
see where we define this in header-inc.php
Code:
Content visible to verified customers only.
and then the css code
Code:
Content visible to verified customers only.
So either your bburl is empty of
vbseo is affecting the setting of variables which is what we have already shared with them.