OCX Controls Used in VBA-Enabled Applications Cannot be Side-By-Side (SxS) Registered

ActiveX Controls used in Office applications with VBA must have at least their type library registered in the registry to work properly.  VBA does not support Side-By-Side (SxS) registration of controls and this may prevent a control registered only by SxS from working correctly in Office.

See the following post for more details:
OCX Controls Used in VBA-Enabled Applications Cannot be Side-By-Side (SxS) Registered