FBA + Alternate access mapping + Workflow task approval = validation errors

Question

This seems like an oddly specific issue that I can't explain.

Issue
In SharePoint 2010.
As an FBA user publishing content, when I attempt to complete a page approval workflow task accessing the site via the 'Alternate Access Mapped' address (e.g. from www.site.com/_layouts/WrkTaskIP.aspx?) I get "validation errors" on the "Requested By" user details (despite the fact that I am infact currently logged in as that same user, who is a site owner and admin).
But if I access using the port number (e.g. Server:1000/_layouts/WrkTaskIP.aspx?, which obviously must be done on the local server machine which isn't an option for regular users) the details validate fine and I can proceed/complete.
(Note: using the Alternate Access Mapped address on the server machine still fails to validate)

Background
I've been trying to do is set up a second FBA User database for a site collection. (Origional FBA users work fine. Logins, edits, publishing and approval, no problem).
I've created the new DB and added the new connection string and membership provider to the site, SecurityToken and Central Admin web.configs. Everything seemed to be working fine; creating new users works, users can log in, checkout, edit etc; and so I assumed everything was done correctly. Since getting the membership provider up and running this is the first, oddly specific, limitation of the new FBA user accounts.

The question
Does anyone know why SharePoint can't validate a valid FBA user when accessing a workflow task via the sites alternate access mapped address (only)?

Answer 1

Solved

I read a very informative article on AAM which helped
Basically I was expecting too much of AAM and there are also several circumstances where things can appear to work for a time/to a certain extent which is what appeared to happen here.

I forgot to set the IIS bindings for the site.

The domain I was using was a test one that we repoint to new sharepoint sites as required so was set up to a certain extent, and adding the alternate access mapping for the test domain seems to work for the most part, but it failed at the point I described above; authenticate the submitting FBA user details when completing a workflow.
Weird.