Not sure if it will help, but you can try using IE7 compatibility mode within IE8. You can try using the torn paper icon to the right of the address bar to enable compatibility mode for just a certain website. It's also possible to go in to the "developer tools" menu item and change the browser mode which forces it to IE7 mode for all websites. We use this to test our software in IE7 and IE8 modes both.
If these companies you mentioned were smart, they would add one line of html code to their website which would force IE8 to compatibility mode automatically. That is described in the link below. Maybe you should pass this link on to the support rep.
http://msdn.microsoft.com/en-us/libr...8VS.85%29.aspx