I hear you…this device has been plagued with network issues, this forum is littered with people complaining about it.
My advice, get current in terms of firmware, and try the various fixes listed in these forums.
What worked for me was disabling the 2 HomeGroup services on every Windows 7 PC. I don’t use homegroup anyway, as I have XP, w7, and ubuntu devices. If I hard power off, the WD still loses the shares, but at least it finds them very quickly now. On a soft power off, it retains. Also make sure the sharing PC is on before you fire up he WD. I have had zero luck powering on a share device and having an already on WD find it.
When this works it is great, I watched a Bluray movie wirelessly last night without any issues, though that is pushing it for this device.