I retested again and chose a page with image files on it and did not see any errors so none of the standard BPS .htaccess code blocks the Bing Sandbox iframe.
I think the smartest thing would be to add a DB Export / Import option. The Security log entry usually tells you what the problem is. ie by looking at the log entry you can see why something was blocked. In this particular case I do not see the cause of the error.