The important part you can test is to open:
http://example.com/.well-known/caldav
and:
http://example.com/.well-known/carddav
in your browser. After you get asked for your username and password there you need to be redirected to a page stating something like:
This is the WebDAV interface. It can only be accessed by WebDAV clients such as the ownCloud desktop sync client.
If that is working it might be possible that your *DAV interface / setup is not working completely / fully. For that we have a FAQ thread available (especially the litmus part there can help you to check your environment):