Webdav on NAS drive

I still can't get a webdav request working. I installed IIS6, created a new
web and connected the home directory to a share on my NAS, ie. \\efs\docs.

Everything works fine but when opening this resouce as a web folder, I
always get an error message or simply nothing to display.

I read a lot of stuff about Webdav and mapped drives, but is there anyone
who got it working?