I am having the same problem, but not having so much luck fixing it. It appears to be doing two different things depending on where you click the image icon in the editor.
The two places I'm referring to are in the Quick Reply and in the Post a Comment option. So far I have created the clientscript folder in the PhotoPost folder and copied the ieprompt.html into it. That helped for the Post a Comment, but the Quick Reply is still a problem.
Also, when I click the image icon in the Post a Comment section, it shows a red x for the ieprompt.jpg image, even though I removed that image from the ieprompt.html file. What else should I change?