To be honest, I don't have a definitive answer four you. From the lack of responses, I don't think anyone else does either. You will probably need to figure this out yourself, because I don't remember ever seeing this behavior before. I would: Try a different theme. Disable all plugins. Try a different resolution, or set GameEx to not change the resolution. Eliminate -autosave -full_screen_brightness 1.1 -cheat from your mame options.I'm not sure if any of the above will help, but we are shooting in the dark here, aren't we?