Windows 7: Win 7 Home machine invisible on network

I have two Win 7 Home x64 machines networked via wireless, and they've been working seamlessly together until a week or so ago, at which point one of them (smilejack1) became invisible to the other (mediabox) and to my Android phone and tablet.

I can access mediabox files from smilejack1 perfectly well, but when I try to access smilejack1 mapped network drives from mediabox, I get this error Message:

An error occurred while reconnecting O: to \\smilejack1\d
Microsoft Windows Network: The network path was not found.

This connection has not been restored

When I try to connect to smilejack1 via mediabox Network Places, I get this error:

Windows Cannot access \\smilejack1.
Check the spelling of the name. Otherwise, there might be a problem with your network. To try and identify and resolve network problems, click diagnose.

Clicking diagnose yields no useful insights.



And when I attempt to use the Sync Me app on my Android products, the scan of my network sees mediabox but not smilejack1.

I should add that I recently lost Internet access on smilejack1, and solving required a registry edit which allowed me to start the Diagnostic Policy Servic, which wasn't running. perhaps this is related?

All help is appreciated.