Reverse proxy acceleration, with authentication enabled, might work fine with Internet Explorer 5.0, but not 5.5. The issue has to do with using an IP address for the accelerator name, and changes in Internet Explorer 5.5. Here's an exchange from a forums user and a BorderManager support engineer.
"We have BorderManager 3.6 running and have always had problems with Reverse Proxy Acceleration and Internet Explorer. When we turn authentication on, IE 5.5 brings up the BorderManager login screen, but ends up failing after trying to login."
"IE 5.5 changed the way it handles authentication requests and how it parses this information. If you want your reverse proxy with authentication to work with IE 5.5, you will have to use the DNS name of the web server, not the IP address. The workstation needs to be able to resolve the accelerator name specified in BorderManager setup to the IP address of
the BorderManager server for HTTP Acceleration with SSL Authentication to work. The BorderManager server needs to be able to resolve the Accelerator Name to the actual IP address of the Web Server being accelerated. For this reason, it is often simpler to put an entry for the Web Server in the hosts file on the BorderManager server.
This issue is resolved by using the hostname and not the IP address setup for the accelerator. This is a requirement for the new session cookie implemented in the BorderManager 3.x; cookie authentication is based on domain name and not IP address.
On the workstation create an entry in the local hosts file for the accelerated site which resolves to the IP address of the BorderManager server. E. G.
xx.xx.xx.xx support.novell.com.au
To access the accelerated site type the URL "http://support.novell.com.au"
And apply the latest fixes for IE 5.5. There is a known bug with IE 5.5 before SP1."