The following error message can occur when trying to use subversion on an apache2 server over https and dav:

501 Method PROPFIND is not defined in RFC 2068 and is not supported by the Servlet API.

The error message is quite misleading. It can be caused by a simple misspelling of the server. In my case I tried to connect to zyx.server.com when the actual address was xyz.server.com.