Each time any user tries to access any Internet resource for the first

time after each login they get this error message:

Not Found
The requested URL /BM-Login/ was not found on this server.

Apache/1.3.27 Server at border_server.westerngraphics.org Port 443

Immediately re-attempting to access the very same resource is
successful.
It continues to be successful until the next time they log out and
then
login again. Any ideas on what might cause this?