Car Pack not successfully installed

I installed the FM5 Meguiar’s Car Pack yesterday and somehow none of the cars were successfully installed. It keeps saying Installing content but it looks like it has stopped. Anyone know how I can fix this?

Try this: http://forums.forzamotorsport.net/turn10_postsm105669_Meguiars-Car-Pack-Cars-given-up-on-installing.aspx#post_105669