This is all down to my lack of knowledge of Apache.
I’ve got several virtual servers running under Apache, with WebDAV enabled on a development site. As part of an investigation into how well i can run ASP under Apache using Mono, I’ve setup another virtual host with mod_mono enabled. The idea is the to enable WebDAV so I can publish from Visual Studio to this site.
Both virtual servers have the same (or similar apart from paths) WebDAV configuration.
WebDAV worked fine on one, but not on another. The other being the VS with ASP running.
It finally dawned upon me that after intercepting any WebDAV commands, apache was then (behaving as it should) giving those commands to mono (SetHandler mono is in one part of the location config). Adding SetHandler none to my WebDAV config sorted the problem – 3 Hours later