I don't know much about slauta93's framework, but I would say that knowing what the server is returning would be very helpful to anyone who can help you with this problem (i.e. what is it returning other than valid JSON - my guess is an error that would lead to the problem).
I have made a debug and saw that there was no json returned, because there was no valid routes found by Symfony2. And with a valid route, there is no json but the page itself returned...
So the sAjaxSource is wrong and i don't understand why... I will continue to learn more about routes in Symfony2 maybe...