Microsoft Internet Controls problem

Every so often the following code breaks, showing
 
  Run-time error '91': Object variable or With block variable not set

It's like the InternetExplorer control doesn't complete the task in time.  If I choose the Debug option then continue execution everything is fine!

Any ideas on what is happening and how to fix it?


Private Sub btnGo_Click()
'On Error GoTo Err_btnGo_Click
' requires Microsoft HTML Object Library
' requires Microsoft Internet Controls

Dim strHTML As String
Dim i As Long
Dim item As String
Dim posted As String
Dim points As String
Dim Qtitle As String
Dim Qhref As String
Dim Mtitle As String
Dim Mhref As String


    Dim appIE As New InternetExplorer
    Dim docHTML As HTMLDocument

    DoCmd.Hourglass True

    appIE.Navigate2 "https://www.experts-exchange.com/Databases/MS_Access/"
     
    'Wait while the page is downloading
    While appIE.Busy
        DoEvents
    Wend
   
    Set docHTML = appIE.Document
   
    Me.Refresh           ' I'm just trying to waste a micro amount of time here
    DoEvents
   
    i = InStr(docHTML.body.innerHTML, "Questions Awaiting Answers")                                   '  <--- this line fails every so often.  Debug it and I can continue with no errors or data loss
    i = InStr(i, docHTML.body.innerHTML, "</TABLE>") + 8
    i = InStr(i, docHTML.body.innerHTML, "<TD class=itemOdd align=right>")
    strHTML = Mid(docHTML.body.innerHTML, i, i - InStr(docHTML.body.innerHTML, "</TABLE>"))
   
    me.txtField=strHTML
 
Exit_btnGo_Click:
    DoCmd.Hourglass False
    Exit Sub

Err_btnGo_Click:
    DoCmd.Hourglass False
    Resume Exit_btnGo_Click
End Sub