Hey MultiColors, thanks for reporting this error.
I think you might be right that this is linked to your RPG Maker version. Would you be able to update your engine to version 1.6 or higher and see if the error still persists? Also could you open the console log (press F8 while the game is running) and post a screenshot of what is written there. That could lend some more insight into what part of the code is not working.
- Neel