For the information of all, hoping will be of some use in solving a
baffling, although apparently rare problem:

Several times over the last year or so, I sought advice in
troubleshooting why only one workstation was not connecting with
clntrust even though a drive was mapped to it on the BM server. There
was no firewall. I finally solved the problem.

I discovered that Norton anti-virus loads a file, sndsrvc.exe, which
apparently acted like a firewall with respect to clntrust. The
offending executable file remained even though Norton anti-virus had
been uninstalled. After running a clean-up program from the Norton web
site, the problem was gone.