Adobe Reader 10.0 is installed in a protected mode. One of the features of the secure mode is:
Cannot open PDF files whose source is DFS or NFS: PDF files in shared locations on a distributed or networked file system (DFS/NFS) cannot be opened. Attempting to open such a file results in an error opening this document. Access denied."
The solution is to disable protected mode by completing the following steps: [more]
Within Adobe Reader, go to Edit > Preferences > General and deselect Enable Protected Mode at startup.
For more information, refer to the following Adobe KB article: http://kb2.adobe.com/cps/860/cpsid_86063.html