LAN PC suddenly not visible to other PCs but can see them as usual

I first noticed that something was wrong with the connectivity of one of my LAN PCs (Windows 7) when my Beyonwiz PVRs stopped listing it. Previously all four PCs (three 7s and one XP) had two-way connection.

I found that the 'missing' PC could see the other three as usual, but the others had lost connection with it.

I have tried another ethernet cable without any improvement. There is, of course, one-way communication, so the problem has probably arisen elsewhere.

One of the other PCs did come up with a Windows Network Diagnostic message: 'Problem found: file and print resource (COMPUTERNAME) is online but isn't responding to connection attempts'.

The question is why this hiccup has suddenly occurred. I would be very grateful for advice as to a fix.

Nobody has responded to this problem as yet. Does this mean that this is an insolated issue being suffered by me alone?

Perhaps this is a physical thing, involving a fault in the ethernet port in the PC (a Toshiba all-in-one still under warranty) or in the ethernet plug in the wall, resulting in one-way communication only?

I have got further info from Windows: 'The remote computer isn’t responding to connections on port 445, possibly due to firewall or security policy settings, or because it might be temporarily unavailable. Windows couldn’t find any problems with the firewall on your computer'.