I was puzzled yesterday when I uploaded a file via WebDAV. Since the file was equipped with a Content-Type header, I expected it to be parsed as reStructured Text. Instead, it appeared as a DTML document. The horror! The horror!

It turned out that the predicate list in the content_type_registry was empty. I don't know why. I recently upgraded the Plone instance from 2.1.0 to 2.1.2, that could be related.

By removing and then reinstalling the ATContentTypes product with the Add/Remove Products tool, the problem went away.

Odd.