You may have opened your Chem3D Substructures file in ChemFinder (maybe unwittingly by double clicking it) and have corrupted it. Please reinstall the Chem3D portion of the software and immediately lock your Chem3D Substructures file BEFORE opening it. If you want to make changes to the Substructures file, use the File/Open command in the Substructure Editor and not ChemFinder.

You may also be having problems building structures because the names they are typing are not defined in Chem3D. For example, "HPsteroid" is probably not defined. The ones that do work, are defined in Chem3D.  You need to open the Substructures table in Chem3D (View menu) and add any substructures that you want to use that are missing.  Alternatively, you could use ChemDraw to build structures, and then copy and paste them into Chem3D.  

ChemDraw offers a number of different ways for easily building structures, including the Name to Structure command, assuming you have a version of ChemDraw that contains this feature.

Also, please make sure you are typing the name exactly as it appears in your substructures table. Try a copy and paste to make sure the name is correct.  Also make sure you do not have more than one substructures table.  It could be that you have more than one installation of Chem3D and you are modifying the wrong table.