I have an iframe-page.html on one server that calls a login.php on another server, which checks users credentials, registers session variables, and redirects to main-menu.php if all successful. Main-menu.php checks for $SESSION_TYPE == 1, if not redirects to error.php.
All works well if iframe-page.html and login.php are on the same server or using Netscape, but is very inconsistant with IE. IE has a successful login, since it is redirecting to main-menu.php; however, the session variables are not being passed from login.php to main-menu.php.
Not a direct answer to your query, but I'd highly recommend you not using any sort of frames/iframes where cookies/sessions are needed (especially across two servers as is your case!).
Session / Iframe problem
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