Fatal Error after 3.7 WordPress Update

Hello to all!
I just updated my wordpress to version 3.7.
Than i realized that my widget area in wordpress has messed up, i can’t do anything on that page, it is frozen.
On my home page where the sidebar widget was placed i get this error now:

Fatal error: Call to a member function reset_postdata() on a non-object in /home/content/39/9088439/html/survivalgeardirectory/wp-includes/query.php on line 118

And also on the home page i don’t see default wordpress admin toolbar.
There’s only a empty area.

Here is the website: https://survivalgeardirectory.com

That is what i have noticed so far, who knows what else broken down.

Can some one help me?
Is there a way to roll back to previous version of wordpress?
For example copy an old installation of wordpress over the files of a new one trough the FTP.

Thank you.