If I set the _"Base skin URL"_ and _"Base media URL"_ to a domain other than the one used for the _"Base URL"_ the image uploader in the WYSIWYG editor breaks.

The _"Media storage"_ popup appears and I can select an image using the _"Browse files..."_ button but any file I select isn't shown in the list and the _"Upload files"_ button does nothing what so ever.

I already checked the JavaScript console and the access/error logs of my server but nothing seems to happen at all.

How can I fix this? Or is this a 'feature' and do I have to disable my custom/cdn url settings just to be able to upload a new image?