Here's a new one on me for you fellow sleuths out there. I was teaching some Word basics to a friend the other night; Word 2010. She had a document that had been converted from a text-editor type application. When I opened the styles pane to explain styles to her, it was completely blank!

I copied the document contents, pasted directly into a new Word doc, and opened the styles pane. It was normal, with a default selection of built-in styles showing.

Any idea what might cause the blank anomaly?