I have already answered your other post on the subject, for convenience I will paste my answer here as well:
The experienced problem is caused by the fact that the ImageEditor is designed to work only with virtual paths to images placed inside its application root (under the same host). Once you configure the control's ImageUrl in the expected by the control way (e.g. "~/Images/image.png") the ImageEditor's dialogs will be loaded properly. Also, please note that the image must be located in a folder accessible from the application.
I hope this information will be helpful for you.
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