Maybe you will took a look
here.
In my opinion:
If you installed a 32bit version of CAD on 64bit system,for example, AutoCAD 2006,you can run
(vlax-create-object "Scriptcontrol") ,it works.
means: Win 64 bit+ CAD 64 bit >> nil
Win 64 bit+ CAD 32 bit >> <vla-object iscriptcontrol XXXX>
Win 32 bit+ CAD 32 bit >> <vla-object iscriptcontrol XXXX>