I had the same issue with 2.65, but the followin helped me to resolved it, thanks for posting it.
SOLUTION Apparently you ran the IIS Lockdown tool. Among other things, it also installs the UrlScanner that adds another protection layer. Unfortunately, this tool filters out any request (to folders) that contain dots.
To overcome this you can edit the urlscan.ini file under C:\Windows\system32\inetsrv\urlscan\ and alter the AllowDotInPath entry from 0 to 1 - AllowDotInPath=1. Thus dots that are not file extensions will be allowed.