I set up a WebDAV folder today to share files in a small office. I had the opposite problem, windows worked fine but linux and OSX would only mount the folder as read-only. Turns out doing autoversioning - putting the whole folder under Subversion (saving a file creates a new revision) was the problem. OSX & Linux want to lock the file but notice apache 2.0 doesn't support LOCK, WindowsXP just writes away. The 2.1/alpha version of Apache has a fix for this, but I haven't tried it yet (I just made a stab at it today).
Autoversioning is the killer feature for me, the other people would/could not use subversion even if they knew what it was. They do like the idea of viewing old versions of files, especially "for free." So I'll be giving Apache 2.1 a try Real Soon Now.