The callback function as described in the documentation for the custom image browser gives an null reference error. I found the solution so here it is for the developers who have the same problem. Maybe it's interesting to update the documentation?
The value of: window.opener.CKEDITOR is null in the IE developer tools.
Changing the callback to: window.top.opener.CKEDITOR fixed the problem.
Version: CKEditor version 3.3.2
Error: 'window.parent.CKEDITOR.tools' is null or not an object
User Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.1; WOW64; Trident/4.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0)
This error occures also on SrWare Iron and Google Chrome.
The value of: window.opener.CKEDITOR is null in the IE developer tools.
Changing the callback to: window.top.opener.CKEDITOR fixed the problem.
Version: CKEditor version 3.3.2
Error: 'window.parent.CKEDITOR.tools' is null or not an object
User Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.1; WOW64; Trident/4.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0)
This error occures also on SrWare Iron and Google Chrome.