It looks like the assembly reference is missing, it doesn't understand which one to use. Theoretically you can try to put <%@ Import Namespace="CMS.DataEngine" %>
...
But I would assume you did an upgrade to your site. Old name space CMS.Controls is not valid anymore, it should be new name space CMS.DocumentEngine.Web.UI. But somehow you still have an old cms.controls in your bin folder and that is why there is confclict between CMS.DataEngine and CMS.Controls. Just check if you have cms.controls in your BIN folder.