img_assist is not able to insert tag or html code

image_assist is not able to insert tag. It gives this error.

Error: uncaught exception: [Exception... "Component returned failure code: 0x80004005 (NS_ERROR_FAILURE) [nsIDOMNSHTMLTextAreaElement.selectionStart]" nsresult: "0x80004005 (NS_ERROR_FAILURE)" location: "JS frame :: http://www.blahblahblah.com/sites/all/modules/img_assist/img_assist_text... :: insertToEditor :: line 89" data: no]

What could be the problem? Thanks