From the screenshots, it looks as if MathJax is running successfully but is producing native MathML output (and you're using Chrome 23 or older).
Even though MathJax uses HTML+CSS output by default, this can be changed and will be stored as a preference in a cookie.
Try right-clicking on one of the formulas to trigger the MathJax context menu where you change the rendering mechanism back to the default HTML-CSS (or the SVG-output).
Deleting the MathJax cookie should help, too.