Problem with Windows shares

I have three computers at home, with shares mounted as shown here.

In general, I can use any computer and can "see" the drives of the other computers.
For example, from computer #1 I can:
-- Use DOS cmd, and type Y: to get to C: on computer #3
-- Use Cygwin bash, and type cd Y:/ to get to C: on computer #3
-- Use Start > Run Y:/ to open an Explorer window to C: on computer #3

All three methods used to work properly from all three computers ... until recently.
Now I have a problem with computer #2 only.
There I can still use bash to do cd Y:/ to get to C: on computer #3 ... or cd T:/ or cd U:/ ... etc.
But DOS Y: fails
And Start > Run Y:/ fails ... or T:/ or U:/ ... etc.
The Start > Run method produces this error:

How can Y: be unavailable? The bash shell can see Y: just fine!

Cygwin is Red Hat's emulation of Linux running on Windows. There are others, but I like Cygwin. It works well.

The shares are for sharing files.
As I said, bash from computer #2 can "see" all the shares. But Windows explorer cannot. And DOS/cmd cannot.
I don't know why it stopped working, and only stopped on this box, not the others.

What other information are you needing?

This happened again. A different laptop, but the same problem. And the same solution:

Code:

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System]
"EnableLinkedConnections"=dword:00000001