I've created a shared addin for Word 2003 in VS 2005 with has a strange habit.
The shared addin creates a commanbar. Everything is working fine, except
that the buttons won't fire if you add new documents in Word. Only in the
available empty document or the last the buttons work, so:

Start Word, only one empty document1 is open, buttons work fine.
Add document by choosing file new -> Document2, buttons don't work in
document2, but in document1.
Close document1, buttons do work in document2.

Who can explain this and more wanted: solve this.

The code for reconstruction: build a addin for Word, keep everthing default
and create this code in Connect.vb

   Private wrdApp As Word.Application (instead of applicationObject as
Object)
   Private mBar As CommandBar
   Private mBarPopup As CommandBarPopup
   Private WithEvents mbarbtnAbout As CommandBarButton

   Public Sub OnDisconnection(ByVal RemoveMode As
Extensibility.ext_DisconnectMode, ByRef custom As System.Array) Implements
Extensibility.IDTExtensibility2.OnDisconnection
       mBar.Delete()
   End Sub

   Public Sub OnConnection(ByVal application As Object, ByVal connectMode
As Extensibility.ext_ConnectMode, ByVal addInInst As Object, ByRef custom As
System.Array) Implements Extensibility.IDTExtensibility2.OnConnection
       wrdApp = CType(application, Word.Application)

       mBar = wrdApp.CommandBars.Add("TEST", , , True)

       mBarPopup =
CType(mBar.Controls.Add(Type:=MsoControlType.msoControlPopup, Before:=1,
Temporary:=True), CommandBarPopup)
       mBarPopup.Caption = "Test"

       mbarbtnAbout =
CType(mBarPopup.Controls.Add(MsoControlType.msoControlButton, , , , True),
CommandBarButton)
       mbarbtnAbout.OnAction = "!<MyAddin1.Connect>"
       mbarbtnAbout.Caption = "Click"

       mBar.Visible = True
   End Sub

   Private Sub mbarbtnAbout_Click(ByVal Ctrl As
Microsoft.Office.Core.CommandBarButton, ByRef CancelDefault As Boolean)
Handles mbarbtnAbout.Click
       MsgBox("Clicked")
   End Sub