Hi,
I have a similar problem with Chrome (newest release). From time to time the page with editor stalls and some warnings occur. This only happens in Chrome and this is not a rule - sometimes page loads correctly.
Clicking the second time on the button refreshing iframe in my website, it is 50% chance that the page & editor will be renderem without any resource errors.
I cannot reproduce it on your demo site. I'm using SSL & iframe.src in my app.
Environment IIS 7.5 Win2008R2 x64, client: Win7 x64, chrome 24.0.1312.57 m
Resource interpreted as Image but transferred with MIME type text/plain: "https://localhost/External/CuteEditor/Load.ashx?type=theme&file=instable.gif&theme=Custom".
Resource interpreted as Image but transferred with MIME type application/octet-stream: "https://localhost/External/CuteEditor/Load.ashx?type=theme&file=colorpen.gif&theme=Custom"
Resource interpreted as Image but transferred with MIME type text/plain: "https://localhost/External/CuteEditor/Images/1x1.gif?634958053705545781".