We've done a number of experiments with different WebDAV setups and this is what we found:
CentOS 5.7, Apache 2.2.3 configured for WebDAV does NOT work. We reproduce the same issues above. 412, Precondition error during update.
CentOS 6.2, Apache 2.2.15 configured for WebDAV works!
CentOS 5.7, Apache 2.2.22, manually built and installed configured for WebDAV works!
For 2.2.15, the following can be referenced for the WebDAV setup:
http://www.cyberciti.biz/faq/rhel-fe...enable-webdav/
For 2.2.22, we used the "OSX" based as a reference for the WebDAV setup. OSX Lion comes with 2.2.20:
http://manas.tungare.name/blog/howto...v-on-mac-os-x/
(The default group for 2.2.22 is daemon:daemon, instead of www:www)
I hope this helps!
Kenton