I saw this old recommendation:
http://www.dnnsoftware.com/forums/threadid/245451/scope/posts/dnn-unc-access-denied-issue-help-please-
You should be able to use this tool now: https://technet.microsoft.com/en-us/sysinternals/bb896645
Sorry that I cannot be more helpful here. This is an area I haven't explored much.
Aderson