I have looked through the articles and message board messages and can't find anything that sounds like the problem I am having. So, if this is a repeat question, let me appologize up front...
Ok, here is the problem. I have an ISA configuration that looks something like this: clients-->ISA-->checkpoint-->ISA-->checkpoint-->internet
The ISA servers are running in Cache mode. When trying to access specific secure sites (requiring a login) I end up with a 401.1 Login Failed error after 3 login attempts. This only happens on the downstream ISA server and clients. The upstream ISA server accesses the site fine. If I point the downstream ISA server's IE proxy settings to the upstream ISA then I can get in fine from the downstream ISA server, but if I point it's proxy settings to itself I can't get into the site again. Again this happens on specific sites...not all secure sites.
I agree that the credentials just don't seem to be making it. I have an upstream rule to allow all IP traffic (it is only in Cache mode) to any site, and then a blocking rule that applies to everybody except the downstream proxy.