Debug Joomla Javascript error

When attempting to insert a pagebreak in the JCE editor the popup box does not display, rather the page navigates to another URL with the pagebreak fields (page name, page title etc). The only lead I have thus far is a Javascript error in Internet Explorer (URL removed): ********************************************************************************** Webpage error details User Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.1; Trident/4.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0; InfoPath.2; Tablet PC 2.0) Timestamp: Mon, 17 Jan 2011 10:27:17 UTC Message: Object doesn't support this property or method Line: 112 Char: 3 Code: 0 URI: [login to view URL] Message: Object doesn't support this property or method Line: 1 Char: 47606 Code: 0 URI: [login to view URL] ********************************************************************************** I require the use of the pagebreak function and need this issue resolved. The URLs can be supplied upon request. I will create a copy of the live site on a sub-domain for fault finding (allowing you to make changes and not disrupting live traffic).