Error in AjaxControlToolkit.ToolkitScriptManager tag

Hi

I have just installed the nopcommerce version 1.5 and when I try to click on the New Product-> product. it shows me the following error. can anybody suggest me what's going wrong with this.  

Type 'AjaxControlToolkit.ToolkitScriptManager' does not have a public property named 'CompositeScript-ScriptMode'.

thanks

This error is because you don't have .net framework 3.5 sp1.  Install .net framework 3.5 sp1.

Thanks

This has resolved the problem.