There are upwards of 40 different variations of webdav client for windows, and you probably have 3 or 4 of them on one machine.
The support for the different clients is very difficult.
There is a newer version of WebDAV support for AOLserver that was never integrated with OpenACS that does have better windows client bug workarounds implemented.
Let me know if you are interested in this new version and I can give you some pointers.