wp-includes/query.php on line 27

Hello all i hope you had a great xmas and new year.

My site http://ukclimber.com
This is a wordpress multisite and buddypress site with bbpress.

The problem:
I have recently updated to wordpress 3.5 and since that time my main site has been having problems. All users are getting the following message when trying to access the main site. Fatal error: Call to a member function get() on a non-object in /home/ukclimbe/public_html/wp-includes/query.php on line 27

This only occurs on the main site and once they are logged in. They can still access there sub site and this problem doesnt occur at all for My super admin account.

I have tried deactiviting all plugins and this changed nothing. I have also tried over writing the wpincludes directory with a fresh install and this did nothing.

I have a feeling its reffering to the roles not being asigned to members in some way but this is merely a guess.

Any ideas anyone?