network installation failed, new diagnostics

[Thomas Wolff <towo@towo.net>]

Concerning https://cygwin.com/ml/cygwin-apps/2016-07/msg00021.html,
I have some new insights; first, I tried with a range of older versions 
of setup.exe (from the cygwin time machine) but all failed, so its not a 
regression as I had speculated.

Then I tried to run setup.exe without elevation, by elevating before 
(running mintty as adminstrator). So I noted (and could have checked 
this earlier...) that the involved network mounts were not fully 
established:

mount (unelevated):
L:/TGI/cygwin7 on / type ntfs (binary,auto)
L: on /cygdrive/l type ntfs (binary,posix=0,user,noumount,auto)
...

mount (elevated):
//141.64.144.100/Labormaterial/TGI/cygwin7 on / type ntfs (binary,auto)
...

After fixing the mount:
net use L: '\\141.64.144.100\Labormaterial'

setup.exe works as expected.

Not being familiar with details of Windows permission stuff and 
user-specific mounts myself, does this help to analyse and maybe even 
fix the situation?
Thanks
Thomas