I checked this problem and find that the point is that the mt.exe may not on your machine.
Since Inventor 2012 we take use of the registry-free tech for the addins, and we updated the InventorWizards to help users to create the registry-free addins easily. The problem you encountered here is that the macro in the post-event of the addin project could not run, and the point is that it will call the MT.exe(manifest tool) is not found on your machine. I guess that you may not have the Windows SDK installed on your machine, and the VS Express version does not include the Windows SDK installer neither. So I would recommend that you download and install the Windows SDK from http://msdn.microsoft.com/en-us/windowsserver/bb980924.aspx, and then try to compile the addin.
The above procedure is from Rocky Zhang from Autodesk Solutions.
When I started Installing SDK, Installation is getting failed and I googled around trying to fix the installation issue.