As Jeff mentiones, IE9 has not been a problem before. But since it is IE, there can be a lot going on.
Since it is not working on both IE and Chrome, can other customers within the same organisation access the content? Also, to which security domain does the URL with the help belong? (Internet, Intranet, custom.) Does the browser report any issues such as error messages that may indicate what is going on?
Kind regards,
Willam