I also use firefox.
If I had to put a bet on it. I'd say that someone was either accessing your reviews at the same time OR someone is submitting a review (anywhere) at the exact same time, thus the database table is indexing and it can't index and load at the same time, thus you either get an error message while checking your reviews, or leaving a new review.
I don't think we can do anything to fix this, but just to get a little more info, if you wait a half-minute or so and then resubmit or reclick on Reviews, does it happen again? IF that's happening, it may be something different, and possibly fixable.
Thanks for your patience while we figure it out.