With that, I can tell you WHAT, but I can’t tell you WHY.
In the case you’re seeing where the “Network” tree doesn’t work or isn’t fully populated, but clicking the STORAGE icon works:
The SMB Master Browser on your network has failed and isn’t responding to “browse” requests.
I just had the same problem this morning after rebooting my QNAP NAS yesterday (which is configured to be the Master Browser.)
When the QNAP went offline, another device on the network should have assumed the browser role – but nothing did. I have eight “potential” browsers, but none of them worked.
Windows had cached some hosts under the “network” tree, but when I clicked them, I got the same erorr you’re seeing.
I don’t know why it happened – the election of another master browser is normally a simple thing. But NONE of my QNAPs, Windows boxes, WD boxes, or otherwise did it.
I had to restart my QNAP again, which then restarted the browser election process, and now my WDTV is the browser and everything is working normally.
I wish I had taken some screen captures like you did while I was fixing it – they looked pretty much like yours.