A simple thread freezes between DoWork and RunWorkerComple ted

I am running an application that, when not used, just sits there firing a
BackgroundWorke r every 20 seconds. Every now and then, the BackgroundWorke r
freezes between the DoWork and RunWorkerComple ted procedures. My simplified
procedures are shown below. They endlessly write messages to a text file.
At some point it never moves from DoWork to RunWorkerComple ted. I do have
services such as Outlook and Norton SystemWorks running in the background.
Any ideas why the BackgroundWorke r freezes between these procedures for no
apparent reason. Could it be some other background service causing the
problem? It has never ran a complete day without freezing.

Each of these procedures has error trapping that shows a message if there is
an error. I never see the message indicating that whatever is happening is
not caused by a trappable error.

Private Sub BackgroundWorke r1_DoWork(XXXX) Handles BackgroundWorke r1.DoWork
C.DoMsg(Now & " BackgroundWorke r1_DoWork -2")
C.DoMsg(Now & " BackgroundWorke r1_DoWork Finish")
End Sub

Private Sub BackgroundWorke r1_RunWorkerCom pleted(XXXX) Handles
BackgroundWorke r1.RunWorkerCom pleted
C.DoMsg(Now & " BackgroundWorke r1_RunWorkerCom pleted Start")
C.DoMsg(Now & " BackgroundWorke r1_RunWorkerCom pleted Finish")
End Sub

Friend Sub DoMsg(ByVal psMsg As String)
Debug.Print(psM sg)
Dim oSW As StreamWriter = New StreamWriter("C :\Temp\AppMsg.t xt", pbAppend)
oSW.WriteLine(p sMsg)
oSW.Close()
End Sub

My code in the timer is:

If Not BackgroundWorke r1.IsBusy Then
Me.BackgroundWo rker1.RunWorker Async()
End If

********Sample log.
6/14/2006 1:13:39 AM BackgroundWorke r1_RunWorkerCom pleted Finish
tmrAutoRecover_ Tick
6/14/2006 1:13:39 AM BackgroundWorke r1_DoWork -2
6/14/2006 1:13:39 AM BackgroundWorke r1_DoWork Finish
6/14/2006 1:13:39 AM BackgroundWorke r1_RunWorkerCom pleted Start
6/14/2006 1:13:39 AM BackgroundWorke r1_RunWorkerCom pleted Finish
tmrAutoRecover_ Tick
6/14/2006 1:13:51 AM BackgroundWorke r1_DoWork -2
6/14/2006 1:13:51 AM BackgroundWorke r1_DoWork Finish
6/14/2006 1:13:51 AM BackgroundWorke r1_RunWorkerCom pleted Start
6/14/2006 1:13:51 AM BackgroundWorke r1_RunWorkerCom pleted Finish
tmrAutoRecover_ Tick
6/14/2006 1:14:07 AM BackgroundWorke r1_DoWork -2
6/14/2006 1:14:07 AM BackgroundWorke r1_DoWork Finish
********Log stops at this point, Application is frozen.