Error page when try to update CSS

When I try to update anything in the CSS – I get sent to an error page it will not update.

I have tried it using a child theme for TwentyEleven, I have tried it using a the TwentyEleven and everytime I press update it goes to an error page.

Also If I try to update my SEO page I get an error page as well? I deactivated my SEO to see if that was the problem but it was not and the problem still remains.

Website is http://healing-path-centre.com/