Is anyone using AutoComplete with Textbox?

I'm in VS 2008 now and I am getting an Exception:

System.InvalidCastException: Specified cast is not valid. at System.Windows.Forms.UnsafeNativeMethods.CoCreateInstance(Guid& clsid, Object punkOuter, Int32 context, Guid& iid)
at System.Windows.Forms.StringSource..ctor(String[] strings)
at System.Windows.Forms.TextBox.SetAutoComplete(Boolean reset)
at System.Windows.Forms.TextBox.OnHandleCreated(EventArgs e)
at System.Windows.Forms.Control.WmCreate(Message& m)

Mind you, I have only set the properties from the Properties pagetab, and they are:

AutoCompleteCustomSource = CA,NY,PA
AutoCompleteMode = Suggest
AutoCompleteSource = CustomSource

Again, this is not code, this is set in the Properties pagetab.