can't edit custom html

I’ve installed the plugin and play a bit with the custom html to create my under construction page. I’ve copy past the html from an existing page and I guess include some code that I shouldn’t as the end of my code is read by WP and integrated in the dashboard (see screenshot)

when I try to click the settings or manipulate the html, it won’t let me save the content. It just takes me to the settings page. And nothing is saved…

Deleting the plugin and installing it back doesn’t help.

How can I get ride of this html code?
Thanks

http://wordpress.org/extend/plugins/ultimate-coming-soon-page/