I just upgraded to IE 5.5 Sp2 or 6.0 and now the Chem3D Plugin does not work.
Microsoft announced that Internet Explorer 5.5 SP2 and above will not support the Netscape plugin architecture. CambridgeSoft is pleased to announce that its Chem3D browser plugin will not be affected by this change. The latest Chem3D Net plugin, v6.0.1, which is now available from our support downloads page, can be deployed immediately to view web pages that contain 3D molecular models. It supports all the common data formats including MDL MOL files and Brookhaven PDB formats.