Wiki Style Broken (vB4)
This is new with vBulletin 4.0.1. Essentially vBulletin "fixed" one of their own bugs by implementing a new CSS system. Obviously this breaks many people's custom styles. We will be releasing Beta 2 much sooner than we anticipated now (which means less new features) because this bug is practically a showstopper.
We have posted a bug report on vBulletin.com which has already been confirmed by the developers and suggests a more elegant alternative than what we are having to do for compatibility with this new system (in VaultWiki 3 Beta 2 keep an eye on your HTML head and you'll see why we complained).