wordpress update 3.5.2 problem

Yesterday I uploaded the 3.5.2 update and now the site is corrupted. I takes several attempts to get to a page and accessing my admin panel is not possible at all. The error message always change but starts with this everytime:

Fatal error: Call to undefined function wp_remote_post()…

The update seemed to failed at first so maybe it corrupted a file somewhere… Where should I start to get this to work properly again?

Thanks everyone