1. "I requery the list on the opening form" - what form is opening - you mean you requery the list on the already open frmAdminstration? That code is in the frmAddUser. Have you step debugged? Under what condition does the code not execute? You could move the code to the AddUser button event following the OpenForm line. Since you use acDialog, the button event code execution will suspend until frmAddUser closes.
Me.lstUsers.Requery
2. Again, step debug, under what condition does the requery method not happen? Consider this code (it works in my test):
Code:
Private Sub cmdDeleteUser_Click()
CurrentDb.Execute "DELETE FROM Users WHERE Id = " & Me.lstUsers
'Requery the Users List
Me.lstUsers.Requery
End Sub