jQuery doesn't seem to be loaded properly on your site.
Could you try to deactivate the NextGen gallery plugin for a few minutes?
If this helps, you can follow the instructions in the NextGen support forums to downgrade to a previous version of the plugin:
http://wordpress.org/support/plugin/nextgen-gallery
http://wordpress.org/support/topic/do-not-uninstall-nextgen-if-you-are-having-issues-with-20?replies=62
Let me know if it helps.