I set up a WebDAV-enabled test site that works perfectly well when mounted and accessed as a drive from XP and Vista clients. It has plain authentication, and SSL is required, using a wildcard certificate. Details: multiple www.example1.com, www.example2.com, etc. domains on a single IP for general HTTP, and webdav1.example.com, webdav2.example.com, etc. for HTTPS using *.example.com certificate.
Mac OS X can mount it too, under Finder/Go/Connect to Server..., https://webdav.example.com, username, password. Mac clients can read all files. But any attempt of copying an item to the site results in a "'webdav.example.com' cannot be modified" error. I tested on a PowerMac with Mac OS 10.4.11, but others tested this on different Mac systems with the same write access problem.
I am not familiar with WebDAVs and Macs. Is this a known WebDAV interoperability issue? Perhaps some server-side setting can be modified to address this? Thanks again.