Server doesn't respond multiple AJAX request at the same time
===

In a website i make, we use arrowchat chat plugin. Arrowchat sends AJAX requests once in around 30 seconds to get the online ppl list.

On the other hand, website's navigation system also uses AJAX requests to get the response from server and load content to a div.

The problem is when arrowchat sends AJAX request, if user clicks a navigation link, browser doesn't send requests until arrowchat's AJAX requests is complete. 

How can i make it run AJAX requests and get respond from server as parallel ?