browse (UNC path to document library) for a specific server problem

For a specific server (test) a) I cannot save use INC path \test\doclibrary. Also:

This is happening for a specific server.

Have tried with other pcs (WIN 8, and 7) with no luck

inside the server (same username), UNC works fine.

Web client is enabled on the PCs and the server

Any suggestions please?