@ana32: did you find a resolution? I’m having the same problem; I discovered that ANY functions.php file in the child directory causes the fatal error. I’m using the twenty eleven theme. (If you delete the functions.php file from the directory in your child theme, then you should be able to get back to your dashboard and site.)
I tried renaming the file to child_functions.php, but then the new functions didn’t load. Does anyone know a solution?
Thanks!