I have been having a problem with user types for the last few weeks.  Trying to open and change any user tyes in the users section of the admin site comes up with this error;

Index was out of range. Must be non-negative and less than the size of the collection.

Parameter name: index

Description: 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.ArgumentOutOfRangeException: Index was out of range. Must be non-negative and less than the size of the collection.

Parameter name: index

Stack Trace: 

[ArgumentOutOfRangeException: Index was out of range. Must be non-negative and less than the size of the collection.
Parameter name: index]
   Umbraco.Courier.BusinessLogic.Tree.CourierAction.get_Alias() +165
   umbraco.cms.presentation.user.EditUserType.BindActions() +552
   umbraco.cms.presentation.user.EditUserType.Page_Load(Object sender, EventArgs e) +1589
   System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o, Object t, EventArgs e) +25
   umbraco.BasePages.BasePage.OnLoad(EventArgs e) +74
   System.Web.UI.Control.LoadRecursive() +71
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +3048

Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.0.30319.1 

Not sure if it is a bug or not... any help would be very very appreciated