On several sites (different configuration) contour security (in section Users) seems to not be working. When expanding the node there are no childs and if one right click > Create, the following error occures in the popup window:

Server Error in '/' Application.
ERROR CREATING CONTROL FOR NODETYPE: formssecurityDescription: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. 

Exception Details: System.ArgumentException: ERROR CREATING CONTROL FOR NODETYPE: formssecurity

Source Error: 

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

Stack Trace: 

[ArgumentException: ERROR CREATING CONTROL FOR NODETYPE: formssecurity]
   umbraco.cms.presentation.Create.Page_Load(Object sender, EventArgs e) +560
   System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o, Object t, EventArgs e) +25
   System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e) +42
   System.Web.UI.Control.OnLoad(EventArgs e) +132
   umbraco.BasePages.BasePage.OnLoad(EventArgs e) +21
   System.Web.UI.Control.LoadRecursive() +66
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +2428








Version Information: Microsoft .NET Framework Version:2.0.50727.3603; ASP.NET Version:2.0.50727.4049