IWebBrowser2::Navigate2 occasionally freezes when opening several new tabs - vba

Question

I'm writing an Excel script to open a list of PDFs in Internet Explorer tabs. It works fine most of the time, but occasionally when I try to close my browser window, a few of the tabs will close, then it stops and all IE instances will freeze, so I have to kill them all in Task Manager. Note that I can avoid the problem by closing each tab individually.
I'm running IE8 and Excel 2007, for the record. Here's my code:
Private Sub Worksheet_BeforeDoubleClick(ByVal Target As Range, Cancel As Boolean)
ShowBrowserWarning
Dim TheHTML As String, PDFs, PDF, First, SerialValue, Test, k
If Target.Column = 1 And Target.Count = 1 Then
' Get the serial number from the adjacent column
SerialValue = Cells(Target.Row, Target.Column + 1)
TheHTML = ShowHTML("http://ucmwww.dnr.state.la.us/ucmsearch/findAllDocuments.aspx?brief=False&query=xwellserialnumber+LIKE+'" & SerialValue & "'+AND+xdocumenttype+LIKE+'WELL ENGINEERING/MECHANICAL'&format=HTML&sortfield=xdate")
Set PDFs = ExtractPDFs(TheHTML)
If PDFs Is Nothing Then
MsgBox "No associated well engineering/mechanical PDFs."
Else
First = True
Dim ie As Object
Set ie = CreateObject("InternetExplorer.Application")
ie.Visible = True
For Each PDF In PDFs
'While ie.Busy
' Dim testvar
' testvar = 1 + 1
'Wend
If First Then
' Open new IE window
ie.Navigate2 PDF.Value
First = False
Else
' Open tab in existing IE window
ie.Navigate2 PDF.Value, 2048
End If
Next
End If
End If
End Sub
What gives? Why does it freeze like that? Does it have anything to do this issue? (Please try not to laugh at my ignorance!) Any help is much appreciated.
Edit: see the italicized text above. I didn't quite describe the problem accurately!

Answer 1

And what about Browser-Busy check? Could it help to avoid the issue?
For Each PDF In PDFs
While ie.Busy
DoEvents
Wend
If First Then
' Open new IE window
ie.Navigate2 PDF.Value
First = False
Else
' Open tab in existing IE window
ie.Navigate2 PDF.Value, 2048
End If
Next
Or just wait between the browser.Navigate calls for a while to give the browser enough time to load one dokument before starting to load next one. Try different time-periods and watch if the freezing issue could be avoided this way.
For Each PDF In PDFs
DoEventsForTimePeriod timePeriodInSeconds:=15 ' try different time periods here
If First Then
' Open new IE window
ie.Navigate2 PDF.Value
First = False
Else
' Open tab in existing IE window
ie.Navigate2 PDF.Value, 2048
End If
Next
Private Sub DoEventsForTimePeriod(ByVal timePeriodInSeconds As Single)
' VBA.Timer: Returns a Single representing the number of seconds elapsed since midnight.
Dim pause As Single: pause = VBA.Timer + timePeriodInSeconds
Do While VBA.Timer < pause
DoEvents ' Yield to other processes.
Loop
End Sub

Answer 2

Well, I´m new too but, as far as can see, I would set ie = Nothing at the end of the sub to loose any relation between VBA and InternetExplorer Application