DOM Exception: INVALID_CHARACTER_ERR (5) [closed]
IE9 was released in March 2011. In the URL you posted, I see the Telerik version is 2010.2.929.40 (September 2010). Perhaps this is just a compatibility issue with the older Telerik version and the new browser? What you can do is either get a newer RadControls build, or force your page to use IE8 rendering. For more information about IE compatibility modes, see http://msdn.microsoft.com/en-us/library/cc288325%28v=vs.85%29.aspx
TL;DR - Add the following meta tag in the header of your page and see if it makes a difference:
<meta http-equiv="X-UA-Compatible" content="IE=IE8" >
From the HTML::DOM::Exception - The Exception interface for HTML::DOM
you can see the reason for this as
INVALID_CHARACTER_ERR (5) If an invalid character is specified, such as in a name.