Upload image button doesn't work

The upload image button doesn’t work.

After clicking the button, there is an error in the Firebug Console:

“ReferenceError: event is not defined
event.preventDefault();

/wp-content/plugins/wp-simple-galleries/wp-simple-gallery-admin.js line 40″

First i thought it was a conflict, but after a fresh WP install 3.5.1. i had the same result.

http://wordpress.org/extend/plugins/wp-simple-galleries/