RUNAS account - Specified Cast is invalid.

When I attempt to look at the properties of a RUNAS account for SQL Server alerting / monitoring which I recently updated to add a new sql server in the distributionl, I get the following error.

Eventually it will come up but the distribution list of servers is no longer populated.

Any ideas?  

Specified Cast is not valid.

Note:  The following information was gathered when the operation was attempted.  The information may appear cryptic but provides context for the error.  The application will continue to run.

System.InvalidCastException: Specified cast is not valid.
   at Microsoft.EnterpriseManagement.Monitoring.Internal.MonitoringObjectGenerated.get_Id()
   at Microsoft.EnterpriseManagement.Common.EnterpriseManagementObject.GetObjectWrappersPostProcessing[T](ReadOnlyCollection`1 resultSet, IEnterpriseManagementObjectCreatable`1 constructorHelper)
   at Microsoft.EnterpriseManagement.Common.EnterpriseManagementObject.CreateMultiple[T](IList`1 dataAccessResultSet, EnterpriseManagementGroup managementGroup, Dictionary`2& instanceById, ObjectQueryOptions queryOptions)
   at Microsoft.EnterpriseManagement.Common.EnterpriseManagementObject.CreateMultiple[T](IList`1 dataAccessResultSet, EnterpriseManagementGroup managementGroup, ObjectQueryOptions queryOptions)
   at Microsoft.EnterpriseManagement.SecurityConfigurationManagement.GetApprovedHealthServicesForDistribution[T](ISecuredData securedData)
   at Microsoft.EnterpriseManagement.Mom.Internal.UI.Common.SDKHelper.<>c__DisplayClass2b.<GetApprovedHealthServicesForDistribution>b__2a(Object sender, ConsoleJobEventArgs e)
   at Microsoft.EnterpriseManagement.Mom.Internal.UI.Console.ConsoleJobExceptionHandler.ExecuteJob(IComponent component, EventHandler`1 job, Object sender, ConsoleJobEventArgs args)

Thanks Lance