Event Validation Error

Hi all,
 
    I am using a datalist in a section on the left side in a page. The panel contains a linkbutton and a image button. On click of any of those i want to update the other section of the page using update panel of ajax. I am using item command event for this purpose. It is working as desired when i click on linkbutton but when i click on image button i am getting a pop up error. It says "Invalid postback or callback argument. Event validation is enabled using <pages enableEventValidation="true" /> in configuration or <%#Page EventValidation = "true" #> in a page."

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