Did you copy ALL of your data files over? If you didn't copy the entire set, you can get that error. All it takes is one missing or corrupted FPT file. You said the program works, though, so the library files sound like they are okay.You could check them by trying to create a new project which would use the existing libraries.
You might also want to reinstall version 3.0 using the option to upgrade an existing version and choose the Typical option so that your library files aren't overwritten. Then make sure that your libraries are okay by creating a new project. If they are okay, you want to make sure that all of your project fiels were copied over -- especially the fpt files. Those are the memo files.