Recently,and my browser and configuration have not changed, hardly any maths formulas are exhibited in the question. Sometimes there is not even a red phrase about an error...nothing to indicate that the formula or symbol is missing. Has the site changed its rendering or something? And this is recent.
OS is Redhat Linux 17 like for years. Browser is Mozilla firefox 37.0.2, like for years. And I didn't have this problem last week...