After upgrading to umbraco v4 rc2 the following line in doc2 form gives null exception error
url = rooturl
+ HttpContext.Current.Request.QueryString["umbPage"].ToString()
+ ("?" + HttpContext.Current.Request.ServerVariables["QUERY_STRING"].Replace("umbPage=" + HttpContext.Current.Request.QueryString["umbPage"].ToString(), "")).Replace("?&", "?")
+ "\nNode ID: " + d.Id + "\n\n";
looks like umbPage querystring parameter is lost. Not sure if there has been a change in the core.