The system disk on my IIS server was filling up, primarily due to the growth in data people were putting out on WebDAV, so I added a disk to the server and moved all of the data to it.
I got the folder targets pointed to the new location and file security fixed.
Each WebDAV folder has a server-local user that logs in via basic authentication
For some reason, however, directory browsing no longer works. People can download individual *files* through a Web browser but when they try to access a directory (wither in a web browser or as a network location), they receive a 403.1 error with the reason "Forbidden: Execute access is denied."
I've done several things to make sure it's not an ACL or other file system permissions issue; it's not. There's something going on in IIS.
Everything was configured properly and woring well before the move to the new disk. In particular, directory browsing is turned on for the WebDAV virtual folders.
The only Windows udates instaleld subsequently were updates to the .NET 4.0 and 4.0 frameworks. These shouldn't affect WebDAV.