CSRF giving problem with ajax

Well, first thanks all for the suggestions!

I found the problem and solution too, my problem was that i had the website accessed from the www and without the www, so my base_url was set with the www and when the users access without the www i give the related problem, so the solution was simple I just redirect all the user to the www url e voila, the CSRF is working better than ever.

Best regards for everyone!