OLE Error: CoInitialize has not been called

Problem/Question/Abstract:

OLE Error: CoInitialize has not been called

Answer:

In a project that needed to display HTML documents, I decided to use the TWebBrowser control. I had used this handy ActiveX control successfully in other projects before.

This application was an MDI application, written in Delphi 5. As a 'specialty' I had installed a beta version of Internet Explorer on my system. I am not sure which of this is responsible for it, but when I would call the function in my application to display the HTML document, the TWebBrowser element could not be instantiated.
Instead I would receive an error message:

'CoInitialize has not been called'

The surprising thing is that the webbrowser control shows fine in design mode! I checked and TWebBrowser was properly installed. The underlieing DLL was also registered properly. A call of

regsvr32 shdocvw.dll

did not help. Finally I manually called the CoInitialize() function. I had to add OLE2 to the list of used units. A good place to do this is the initialization part as the sample snippet below shows.


uses
  OLE2, // <-- make sure to include this unit
  Windows; // and others

initialization
  CoInitialize(nil); // <-- manually call CoInitialize()

end.