Turned out I was missing the file itself file C:\Program Files\Microsoft Visual Studio 9.0\Common7\IDE\Microsoft.JScript.AuthoringServices.dll and a complete search of the hard drive yielded nothing. Don't know where the file went as Intellisense used to work, but it simply wasn't there.
So I emailed the readify internal techlist and the file was delivered to my inbox shortly thereafter. Once I copied the file to its correct location, everything worked again.
Interestingly, another colleague mentioned that the file did not exist on their system either. I am running VS2008 in a virtual PC but don't know if that had anything to do with it.