Why are some resource not reciving MSProject notification when they should

We have a few MS Project Server users who are not receiving any notifications of tasks changes when their task is updated or when a new task is assigned. I have checked their notification settings and they have correctly set them so they should recieve them.

I took a look in the error log and found the errors listed below. If anyone out there has any ideas, that would be greatly appreciated.

(0x0BA4      Project Server                      Project Server Server-Side Even      6660      Critical      Event Handler for event "NotificationsSending" of type "NotificationsEventHandler.MyNotificationsEventReceiver" threw an exception: Notifications Sending PreEvent failed. Exception: System.IndexOutOfRangeException: There is no row at position 0.     at System.Data.RBTree`1.GetNodeByIndex(Int32 userIndex)     at System.Data.RBTree`1.get_Item(Int32 index)     at System.Data.DataRowCollection.get_Item(Int32 index)     at NotificationsEventHandler.EventHandlerCommon.GetResourceEmail(Guid resourceUid)     at NotificationsEventHandler.EventHandlerCommon.SendMyNotification(String eventSourceName, String eventName, PSContextInfo contextInfo, EventArgs args)    at NotificationsEventHandler.EventHandlerCommon.SendMyNotification(String eventSourceName, String eventName, PSContextInfo contextInfo, Eve...       )

(01/06/2010 14:32:57.59*      Microsoft.Office.Project.Server (0x0368)      0x0BA4      Project Server                      Project Server Server-Side Even      6660      Critical      ...ntArgs args)     at NotificationsEventHandler.MyNotificationsEventReceiver.OnSending(PSContextInfo contextInfo, NotificationsPreSendEventArgs e)       )