"Publish" button doesn't work

Suddenly the "publish" button doesn't work for the Post in one of my clients site: http://www.matertraining.com
When you hit "publish" it schedules the post and it remains that way forever and if you try to publish the post from the post page there is no way to do it. If you hit "publish" changing the status in the post list, it doesn't work either and it remains in "scheduled status".
The only way to publish a post is to "schedule" to day before which is something really weird and makes useless the "schedule feature". Any idea in how to solve that?