getting error while opening a popup through ScriptManager.RegisterClientScriptBlock

Question

hi i have a gridview inside an updatepanel, in the gridview i have image buttons on click of which an popup should open, but instead an javascript error occurs as 'sys.webforms.pageRequestManagerServerErrorException: Invalid Postback or callback argument. Event Validation is enabled using in configuration or <%@Page EnabledEventValidation="true"%> in a page for security purposes this feature verifies that argument to postback or callback events originate from the sever control that originally rendered them...' code for opening popup is string popupScript = "" + "window.open('./Myform.aspx','Myform', 'top=100,left=100,width=1000, height=800, menubar=no, resizable=no, status= yes, scrollbars=yes')" + ""; ScriptManager.RegisterClientScriptBlock(this, this.GetType(), "MyForm", popupScript, false);

let me know if i am missing something...