Fatal Error when Activating Advanced Theme Switcher

Hi,

I’m trying to activate Advance Theme Switcher but I get the following error:

Call to a member function get() on a non-object in /dir/wp-includes/query.php on line 27

I’ve tried disabling all plugins one by one to check conflicts, return to default wordpress theme.

Non seem to work. Same error.

Anything else I can try?