This is not something a person would make up off the top of their head. How did you arrive at the solution? (Assuming something other than looking at logs, or you would have said.)
And, equally important: Why is MSIE (only) sending in this form of request in the first place? Is it simply the browser's way of saying "I have no idea what this extension means, so please tell me more?" I'm always intrigued by questions that have server-side solutions although the problem only occurs in one browser.
For anyone else whose immediate reaction was "What the ### is PROPFIND?": [webmasterworld.com...]
Apache itself grudgingly hints that it's got something to do with mod_dav, but beyond that point it's stubbornly silent. Unless you count
The PROPFIND method retrieves properties defined on the resource identified by the Request-URI, if the resource does not have any internal members, or on the resource identified by the Request-URI and potentially its member resources, if the resource is a collection that has internal member URIs.