Compatibility with vBulletin 4.2.1
In vBulletin 4.2.1, the base class for the activity stream was changed dramatically such that VaultWiki 4 has a fatal error on the page. The issue is fixed in the next release of VaultWiki, but the change means that VaultWiki won't work on 4.2.0 anymore, only 4.0.0 - 4.1.12, 4.2.1+