Blank child theme – functions.php problem

I’ve created a child theme, and moved all the modifications I had in
the parent theme functions.php into the child theme’s functions.php

Don’t move all the functions from the parent theme into the child theme, just add the modifications to the child theme and leave the parent functions.php as it came with the theme.

You are most likely loading the functions twice as a result.

Unlike style.css, the functions.php of a child theme does not override
its counterpart from the parent. Instead, it is loaded in addition to
the parent’s functions.php. (Specifically, it is loaded right before
the parent’s file.)

http://codex.wordpress.org/Child_Themes#Using_functions.php