ReportViewer in my aspx page giving an error

I draged and droped a ReportViewer in my aspx page then tried to debug the page. I got this error "Error: Sys.ArgumentNullException: Value cannot be null.
Parameter name: panelsCreated[1]" I noticed that its because i have the AjaxControlToolKt assembly. Is there another way to solve this with out having to remove the AjaxControlToolKit file? 
Help this the first time am creating reports