It sounds like a problem with the installation - perhaps the templates used to create the generated code did not get installed properly. Can you tell me which version of the Instrument I/O Assistant you have installed? You can do this by looking in the <National Instruments>\MAX\Assistants\ directory and looking at the properties IIOA.mxw. It should be either version 1.0 or 1.0.1.
If you have version 1.0 - look in the same Assistants directory and see if there is a file named IOScriptor.LLB. If you have version 1.0.1, look in your <LabVIEW 7.0>\vi.lib\ directory and see if there is a InstrIOAsst directory with an LLB named IIOA.LLB. (The name and location of this LLB changed between these two releases) These are the VI templates used to generate the code behind the Express VI - I am assuming you are probably missing this LLB. Also - to answer your question about the "Code generation type" option - it is only active when VISA knows the currently selected instrument is available over the GPIB bus. If it is not connected over GPIB or if the resource name is invalid than GPIB code generation is not an option. This is probably why the option is invalid.
