Specified cast is not valid error

Hi Experts,

Can someone tell me why the 'Do Until' line is causing a 'Specified cast is not valid' error?

    Private Sub BackgroundWorker1_DoWork(sender As System.Object, e As System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork

        WebBrowser1.Navigate("http://www.yahoo.com")

        Do Until WebBrowser1.ReadyState = WebBrowserReadyState.Complete
            Threading.Thread.Sleep(10)
            Application.DoEvents()
        Loop

    End Sub

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DColinAsked:
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Rikin ShahMicrosoft Dynamics CRM ConsultantCommented:
Hi,

The thing is that the WebBrowser control is designed to work in one thread only.
http://mkartak.blogspot.com/2010/02/working-with-webbrowser-control.html

You (can) get this error when calling on the WebBrowswer control from a non-GUI thread. You need to Invoke the webbrowser control as it is not thread safe.

In general, you use webBrowser1.Invoke(). You'll need a delegate and probably some other thread control since you are trying to pause there. You can read about Invoke and InvokeRequired on MSDN.
http://msdn.microsoft.com/en-us/library/zyzhdc6b.aspx
http://msdn.microsoft.com/en-us/library/system.windows.forms.control.invokerequired.aspx
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