Proxy and ISAPI extension not configured error

[Peter Schober]

* Istvan Gonzales <istvangonzales at gmail.com> [2012-08-24 06:04]:
> Is there some obvious misconfiguration that can be responsible for
> their issue, specifically that users can log in properly if
> accessing the website directly, but they get the below error when
> logging into a protected area when using a host entry to the proxy?
> Non-protected areas of the website work fine.

Everything is possible then a "proxy" is involved.
-peter