WebServer not replying to GET/POST requests until previous request is finished

I have a Web Server that provides reports and other different applications and usually these reports are huge and it takes several minutes for the Server to reply to this POST Request, so I've noticed when the report is being generated and I'm still waiting for the POST response I can't do anything else on the webserver until it finishes.

If I try to access another menu, the server would wait until it has finished answering the report POST response, and then answers my other requests.

Also, I've tested with different users logged in and it seems they can access the server normally while the report is being generated. So I wanna know is this normal behaviour or it could be related to user access to the webserver.

BTW Server is using Symfony Framework 2.0.9