Cookies makes Ajax ASync treat like Sync

Hello,

I moved an existing project into the CodeIgniter Framework. 

If I try to click on a link during JQuery Ajax Request which is still loading, I can't do anything on the page, meaning I can not click any other link.

However this happens only with Chrome and IE Edge. No issues with Firefox.

I installed the chrom web-developer addon http://chrispederick.com/work/web-developer/chrome/ and disabled all cookies.
When everything is disabled, it works like a charm.

I know this are not pretty much details. But can you help me? I even would like to invite you in a team viewer session to solve this problem. Of course i would pay you as well.

Need to get this done until tomorrow.

Thanks, 
Stansolo