I have the same issue.
WIth clean install of WP > No problem
After I installed Dante and installed plugins suggested by the theme, this issue occurs.
I deactivated all plugins then it works.
I deactivated one by one but i was not able to figure out which one was causing this problem because after disabling one plugin it worked and after a while is started not to work.
Which plugin can cause it, you are supposed to have more experince about it.
thanks

Theme:Dante
WP: 4.0
Installed Plugins: see attachment

thanks