You may be having a conflict with another set of Strata's Photoshop plug-ins. You either have two different sets in the Photoshop Plug-ins folder, or an older set.
Go to the Photoshop Plug-ins folder and make sure that you have an alias that points to the "Strata D3D CX 3D[in] Plug-ins" folder in your Strata Design 3D CX 6 folder.
If you see another alias similar to this pointing to a folder in Strata 3D CX 5.x, you'll want to remove this alias.
The plug-ins might also be in a folder named "Strata" within the Ps plugins folder. If you have this folder, remove from it the following files: StrataImport.plugin, StrataModeler.plugin, StrataRender.plugin, StrataViewMatch.plugin.
If that "Strata" folder only contains the four files I mentioned, then you can delete it as well.