VBA: Please Help. Runtime Error during "DoEvents Loop"

[Peter h]

Hey guys, I'm hoping someone can help me out here. I'm manipulating a webform with a userform for work. I'm getting a Run time error 91: "Object Variable or With block variable not set." on the highlighted line of code.

Set IE = New SHDocVw.InternetExplorerMedium
IE.Visible = True
IE.Navigate Nav
Do
    DoEvents
Loop Until IE.ReadyState = READYSTATE_COMPLETE

Set WF = IE.Document

With WF
    .getElementById(SType).selectedIndex = Me.ListBox1.ListIndex + 1
    .getElementById(SType).FireEvent ("onchange")
End With
Do
    DoEvents
Loop While WF.getElementById(CROList) Is Nothing

Set e = WF.getElementById("ListBox1")
i = 0
    For Each o In e.Options
        If o.Value = Me.TextBox2.Text Then
            e.selectedIndex = o.Index
            e.FireEvent ("onchange")
            Exit For
        End If
        i = i + 1
        If i > e.Length Then
            MsgBox "Sample was not found."
            Exit For
        End If
    Next o
Do
    DoEvents
[COLOR=#FF0000]Loop Until WF.getElementById("btnAccept").Disabled = True
[/COLOR]
If Me.CheckBox1.Visible = True Then
    If WF.getElementById("Incl_Daily_Average").Checked = True Then
        Me.CheckBox1 = True
    Else
        Me.CheckBox1 = False
    End If
End If
IE.Quit
Set IE = Nothing

When I step through the code I don't get the error. It's only when I try to run the code. Any ideas?