1. What is http://server.domain.com:8000/ ? Is this a Load balancer or Proxy server ? Were you using SSL termination ?
2. After making the changes to disable SSL, you ran autoconfig and restarted all eBiz middle tier services ?
3. Take a look at "Step 8 - Update the Context File" in "Enabling SSL in Oracle E-Business Suite Release 12" (Doc ID 376700.1) and make sure your $CONTEXT_FILE has all the correct values listed under "Non-SSL Value"
Thanks for your reply.
I found the problem, every thing was OK.
The problem was with IE8, new feature of using same session for multiple visits to same site.
I just use new session , it was working.
Thanks for the update and for sharing the solution.
You may also take a look at the following docs.
R12: Using IE8 to access two EBS Instances runs in error "Unable To Authenticate Session" (Doc ID 1098563.1)
Recommended Browsers for Oracle E-Business Suite Release 12 (Doc ID 389422.1) -- Multiple Sessions