Word automation that work in an .exe and not in a .dll

[DJ]

Hi,
I have this piece of code that work well in an .exe. If I move this
code to a function in a dll and have an .exe calling the function, an
exception is raised : The server threw an exception. Why the same code
is not working in my dll??? The error occurs with the first call to
the InsertFile function (and yes the files that I insert exists). In
fact any call to Doc.Words.First is throwing an exception.
Dim App As Word.Application
Dim oMissing As Object = Missing.Value
Dim PageBreak As Object = Word.WdBreakType.wdPageBreak
Dim visible As Object = False

Try
App = New Word.Application
App.Visible = False

Dim Doc As _Document = App.Documents.Add(oMissing,
oMissing, oMissing, visible)

For Each FName As String In FNameArray
Doc.Words.First.InsertFile(FName)
Doc.Words.First.InsertBreak(PageBreak)
Next
Catch ex As Exception
Resultat = False
Finally
Dim saveChanges As Object = True
Dim originalFormat As Object = Missing.Value
Dim routeDocument As Object = Missing.Value

App.Quit(saveChanges, originalFormat, routeDocument)
End Try
Thank you!