There is no semicolon on that line.
From my experience, a missing semi-colon throws a 500 error.
Unless I'm misunderstanding something, since that could be re-written like this there is a semi-colon.
add_theme_support('genesis-custom-header', array('width' => 960, 'height' => 120));
The error says there is an unexpected semi-colon. If I had to guess, I would say that an entire line was moved into another, including the semi-colon, which was then superfluous. So maybe it had looked like this:
add_theme_support('genesis-custom-header', array('width' => 960, 'height' => 120););
It would help to have the lines around the one generating the error to get a better idea of the bigger picture.
As the thread has been marked Resolved, I presume the extra semi-colon was found.