Using Interop.Outlook in a seperate thread

Hi All,
I've got a bit a problem I can't seem to work out.

Using the code listed below, the program runs fine within the VB dev
environment, but once built and running outside of VB, it doesn't

Public Sub StartRefreshingEvents()
Dim th As New System.Threading.Thread(AddressOf
RefreshTodaysEvents)
th.Priority = Threading.ThreadPriority.Lowest
th.Start()
End Sub
Private Sub RefreshTodaysEvents()
Msgbox("this line never runs outside VB dev program")
Dim oApp As New Outlook.Application
Dim oNS As Outlook.NameSpace
Dim oCalendar As Outlook.MAPIFolder
Dim oItems As Outlook.Items
'blah blah blah.......

Its definitely running the th.start() but never runs the msgbox line I
put in while running as a stand-alone app....run it within VB and all
is fine.

Is it something to do with the Reference to Outlook ?

TIA
Scott