'null' is null or not an object

I am using gwt with struts2. I get a javascript error in IE. It works
fine in firefox and chrome.I got this problem only in IE.I tried in
IE7 and IE8. Here is the javascript error i get.

Webpage error details

User Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.1; Trident/
4.0; .NET CLR 2.0.50727)
Timestamp: Fri, 3 Jun 2011 02:35:47 UTC

Message: 'null' is null or not an object
Line: 2487
Char: 42
Code: 0
URI: http://192.168.1.101:8080/Nexus/89F0B25E34680577B6A25648F31A52ED.cache.html

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