Authenticate user - HTTP/1.1 500 Server Error

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When using Authenticate User behavior I get HTTP/1.1 500 Server Error. Only
on remote server, not localhost. The host first tried to tell me it was
because I was using Access, that my db wasn't working, but I showed them that
it did work on pages without the behavior. I feel like I'm getting the
runaround. Anyone else have this problem? Any ideas on how to help would be
greatly appreciated.
Thanks.
Sally

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I just realized that when the login page is submitted, not only is the page
not going to the "if succeeds" page, the domain name appears in the URL twice -
i.e. [url]http://mydomain.com/mydomain/Residents_LogIn.asp[/url]. This is the URL that is
giving the 500 error. The page is not going to
[url]http://mydomain.com/Residents_Profile.asp[/url].

On my local server it goes to [url]http://localhost/mydomain/Residents_Profile.asp[/url]

I can't see anything in the code that would cause this. I'll submit it if
anyone wants to see it. I don't know if this makes a difference, but the
hosting site allows multiple domains to be hosted, you just put in what
directory you want them to point to on your server. So this is in a "mydomain"
directory. But all the other pages work fine, and so does this if I don't have
the Authenticate User behavior on it.

Any ideas? I'm totally stuck! Thanks.