First, see if the first post of this link helps you: http://community.wd.com/t5/WD-TV-Live-Streaming/How-to-resolve-quot-Network-shares-quot-access-problems-with/td-p/671513
Secondly, you could have a master browser problem that comes and goes with devices going on and off. See this, download the free program so see if your main PC is always the master browser when it is on.
http://scottiestech.info/2009/02/14/how-to-determine-the-master-browser-in-a-windows-workgroup/
It is possible for some routers to be the master browser, and that can eliminate the problem. It did for me.
