WebDAV: Not every 403/Forbidden means wrong credentials
When a contact is dragged&dropped from one address book to another, EDS issues PUT. The server can answer to this with 403 Forbidden: no-uid-conflict precondition. Whether this answer makes sense from the server is a different question. In turn, Evolution asks for new password. This is an endless loop. Evolution shall offer in such cases the possibility to cancel the copy (or perform HTTP MOVE).