Either you:
- Don't have installed with the current version of the installer
OR
- You manually tried to replace files from a previous version, and this will never work.
All files from a certain GSX release must come from the same version, and they are always all installed together with a full installer, so it's not possible to get them mixed up by mistake. The only possible explanation of that error, is that you have placed files from a previous version.
You should be able to "clean-up" the installation, by replying YES to the question "Do you want to remove the Couatl scripting engine ?" made at the end, then reinstall using the full installer, and don't add/change anything.