My first guess is you're trying to use server license instead of node-locked license. Starting from Creo 8.0, PTC has separated Flexnet (license server) installer from the main installer and standalone Creo installer (setup.exe) recognizes only non-floating license files.
In the installer folder, you also should have install_license_server.exe (or similar). Run that and provide your license file, it should install correctly, and then you can run Creo installer. It should pick up the existing floating license and continue with installation.
