Aha! I forgot about one bug I encountered in the setup. It installed VSTO for Office 2003. I never had Office 2003 installed on it. The version of Office installed on my machine is Office 2007. Setup went ahead to install its VSTO version for Office 2003 and latter on complained that some functionality (actually most) will not work unless I installed Office 2003.
The question is: I didn’t have the right version in the first place, why install something that will not be supported? It should have detected the correct version.