Yup! It happened a few times when I was reading a fic in French. I hate grammar/spelling errors. I mean, a few are ok, because you and your beta can miss one or two while re-reading it. But too many? No! I've said it once for an fic in English because though it's not my first language, I can see mistakes.
But god, sometimes with fics in French... Once I even wanted to change everything in the fic 'cos I so thought the author never watched Atlantis! (it was a Pretender/Atlantis crossover)