It takes the interaction of three web pages for the problem to show up:
1) a php file with session_start() and a form (Post Method) pointing (action) to file 2. 

2) Once the form in file 1 is submitted we get to php file 2.  File 2 also uses session_start() and links to file 3.

3) we are in file 3 and try to get back to file 2, I get this message from internet explorer instead of file 2.

"Warning: Page has Expired The page you requested was created using information you submitted in a form. This page is no longer available. As a security precaution, Internet Explorer does not automatically resubmit your information for you. 

To resubmit your information and view this Web page, click the Refresh button."


This situation does not happen when:
1) Use "session_start" and "get method" on file 1)
2) use "post method" but do not use "session_start". So it looks like the problem is with the "session_start" function.

I replicated the same programs with .asp (microsoft) (e.g. using session handling and post method) and no problem.

I hope this helps,

Alejandro Ramirez
Caracas - Venezuela