My phone recently rebooted itself and afterwards my accounts were gone, including my DavDroid-Sync (probably not a DavDroid problem though). So I tried to reattach it to the OwnCloud installation I was using before - in the meantime I received an update to version 0.6.11, so the error might be related to that update.
What I did: entered correct server info, user name and password.
What happened: “401 Unauthorized”, no log entry on the server (neither in access.log nor in owncloud log) so apparently no connection attempt happened.
Things I tried: changing the folder, using HTTP, installing the server’s root cert. Nothing helped.