Brian,
Thanks for the reply. I found this TechNet article that seems to confirm that Windows 7 and Windows Vista both ship with 'Basic Authentication' switched off. This article details how to switch it back on again:
*here*
However!
Switching it back on is a little involved and has unknown consequences for security beyond webDAV, so I would like to establish whether openACS webDAV support can be configured to use digest authentication. If not, as it is written in tcl it is not beyond the realms of possibility that I could add it, but I'd probably need some guidance for sources of information.
Regards
Richard