I use reverse proxy for authentication to an Intranet from the Internet
when users are home. This has been in place for many years. There are
always a few who have some difficulty in authenticating. Most
authenticate OK. Others get the message "you are already logged in" and
cannot access the Intranet.

Using BM 3.9 sp1. Using a high port - 1444.

Any ideas what could cause this? Could it be the ISP of some?