有没有人遇到以下错误？它似乎是间歇性的，但无法追踪问题。
System.Runtime.InteropServices.COMException (0x8007057F): Cannot find window class. (Exception from HRESULT: 0x8007057F)
at mshtml.HTMLDocumentClass.IHTMLDocument2_get_parentWindow() at WatiN.Core.Native.InternetExplorer.IEElement.get_ParentWindow()
at WatiN.Core.Native.InternetExplorer.IEElement.GetJavaScriptElementReference()
at WatiN.Core.Native.InternetExplorer.IEFireEventHandler.CreateJavaScriptFireEventCode(NameValueCollection eventObjectProperties, String eventName)
at WatiN.Core.Native.InternetExplorer.IEFireEventHandler.FireEvent(String eventName, NameValueCollection eventProperties, Boolean noWait)
at WatiN.Core.Native.InternetExplorer.IEElement.FireEvent(String eventName, NameValueCollection eventProperties)
at WatiN.Core.Element.FireEvent(String eventName, Boolean waitForComplete, NameValueCollection eventProperties)
编辑：这是在Windows 7上使用IE9