from time to time, my monitoring application dies for no obvious reason. It seems like "mshtml.HTMLDocument" resource isn't available. Anyone else experienced something similar? Thanks in advance.
Error message:
14.04.2011 18:26:37 -> Test 1.2 (Subscriber type requests), error: Unable to cast COM object of type 'System.__ComObject' to interface type 'mshtml.HTMLDocument'. This operation failed because the QueryInterface call on the COM component for the interface with IID '{3050F55F-98B5-11CF-BB82-00AA00BDCE0B}' failed due to the following error: No such interface supported (Exception from HRESULT: 0x80004002 (E_NOINTERFACE)).
Error stack trace:
14.04.2011 18:26:37 -> Test 1.2 (Subscriber type requests), trace: at WatiN.Core.Native.InternetExplorer.IEWaitForComplete.WaitForFramesToComplete(IHTMLDocument2 maindocument)
at WatiN.Core.Native.InternetExplorer.IEWaitForComplete.WaitForFramesToComplete(IHTMLDocument2 maindocument)
at WatiN.Core.Native.InternetExplorer.IEWaitForComplete.WaitForCompleteOrTimeout()
at WatiN.Core.WaitForCompleteBase.DoWait()
at WatiN.Core.IE.WaitForComplete(Int32 waitForCompleteTimeOut)
at WatiN.Core.Browser.GoTo(Uri url)
at WatiN.Core.Browser.GoTo(String url)
at WebMonitor.Tests.Execute() ...
Thanks for reporting. I have put a a re-try around the cast. This exception is probably caused by timing. Hope the re-try will fix it. Will be part of the next release or get the latest code from SourceForge.
来源：https://stackoverflow.com/questions/5664880/watin-unable-to-cast-com-object-exception