Same-Origin-Policy error with lightbox

[Bugfix]

Hello!
XF has an integrated lightbox. I only add LbTrigger-Class and a data-href-Tag and the lightbox is working - great!
But I have one issue: I sometimes (its a feature for users) call my page via subdomain - then my browser prohibits lightbox to load and fires a same-origin-policy error:

Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at http://www.mydomain.com/misc/lightbox?&_xfRequestUri=%2F&_xfNoRedirect=1&_xfToken=xxx&_xfResponseType=json . This can be fixed by moving the resource to the same domain or enabling CORS.

Summary:
Call http://www.mydomain.com/myaddon/123/view -> lightbox works
Call http://anysubdomain.mydomain.com/myaddon/123/view -> lightbox fires cross-origin request blocked

Any ideas?
Thanks, Harald

 

[MattW]

Similar issue to this : http://xenforo.com/community/resources/audentio-adstyler-cdn.3023/

 

[Bugfix]

Thanks, but unfortunately I tried this befor with no success.
Thank you anyway for your help!