Goolge 1 plugin: Settings problem

I go to wp-admin

click settings

click on Google +1 Button Settings

currently the checkbox for “Show the +1 button on posts” is checked

but I can’t uncheck it

anytime I click (to uncheck) and hit “Save”, the checkbox is still checked.

Is there something I am doing wrong?

http://wordpress.org/extend/plugins/wp-plus-one/