My IT crowd couldn't find a problem, but I'll tell you how I got around it:

I used the following code instead:

Sub Open_SaveItem()

Dim objApp As Outlook.Explorer
Dim objSelItem As Object
Dim objSelection As Outlook.Selection
Dim strSubject As String
Dim dteDate As Date
Dim dteTime As Date
Set objApp = Application.ActiveExplorer
Set objSelection = objApp.Selection
SaveAsFile.Show
Set objApp = Nothing
Set objSelItem = Nothing
Set objSelection = Nothing

End Sub

Note that the only three changed lines are:
Dim objApp As Outlook.Explorer
Set objApp = Application.ActiveExplorer
Set objSelection = objApp.Selection

Which were:
Dim objApp As Outlook.Application
Set objApp = CreateObject("Outlook.Application")
Set objSelection = objApp.ActiveExplorer.Selection

I think this means that the code is using the current Outlook app as default.

I hope this helps someone!

Regards,
Jeff Popova-Clark
Gold Coast, Australia