Exporting for Arnold is denied. Message saying failed to save presets, no permission to write.

Hi there, im new in substance. So while working in my second model (never had an issue with the first one), I´m trying to export the textures to an AiStandardshade from Arnold, but every time i getting this message:

[Library agent] Failed to save updated preset 'Arnold (AiStandard)': The default library 'starter_assets' is only available in read mode because you don't have write permission on it.

I just checked and none of the presets are available to export. So I reintalled the program two times and deleted all files installed in documents and nothing, this continues to happen every time. Any one knows how to override this? 

Thanks!