New version polished of all errors and now compatible with all versions of RTW.
This is a standalone version. You must delete the old version, otherwise this won't work.
Simply unzip the downloaded file and put the "bi-attila" folder inside your main RTW directory ( where the .exe files are ). Then on Your Steam library:
1.right click on Rome Total War
2. Click "Startup options"
3. paste this text inside the window=> -show_err -nm -mod:bi-attila
4.Start Barbarian Invasion normally.