Broken dashboard

All of a sudden this afternoon we started getting this error on our wordpress site.

Fatal error: Class Requests_Cookie_Jar contains 1 abstract method and must therefore be declared abstract or implement the remaining methods (IteratorAggregate::post_parent) in E:\Apache2\htdocs\nwgvcop\wp-includes\Requests\Cookie\Jar.php on line 15

There have been no updates to the site today and it ran fine after a minor update to the pop-up maker plugin yesterday.

The error is preventing anyone from accessing the dashboard of the site. One blogger was creating a post at the time, but besides that nothing else was going on at the time of the crash.

The site is using twenty-twelve with a child theme, buddypress, and bbpress plus several plugins to support buddypress functionality.

This error seems to be the WordPress core, any ideas on how to fix this?