[Exception… “Could not convert JavaScript” nsresult: “0x80570009 (NS_ERROR_XPC_BAD_CONVERT_JS)”

What the heck is..

uncaught exception: [Exception… “Could not convert JavaScript argument arg 0 [nsIDOMHTMLDivElement.appendChild]” nsresult: “0x80570009 (NS_ERROR_XPC_BAD_CONVERT_JS)” location: “JS frame :: PATH_TO_MY_JAVASCRIPT_FILE :: THE_METHOD_NAME :: line #” data: no]

For me it was just an appendChild() that was causing the problems. You can always try the innerHTML+= way if all else fails 😉