Try this,
Get a copy of the exact same version of MODX you installed.
Copy the core, manager, setup, and connectors directories to your site.
Be careful not to overwrite the following files:
core/config/config.inc.php
config.core.php
manager/config.core.php
connectors/config.core.php
setup/includes/config.core.php
Delete all files in the core/cache directory
Clear your browser cache and cookies.
If everything works, you're good to go.
If not, run Setup in upgrade mode.
When everything is working, delete the setup directory.
