I booted into safe-mode, and while there I uninstalled Outlook and Hotmail (its predecessor, which is now obsolete and no longer works anyway). I also cleared the data from my contacts and contactsdata apps.
When I rebooted, the contacts app is now working and doesn't force close! So, now I know how to fix it. I'm going to try to reinstall the Outlook app (perhaps Outlook and Hotmail's syncing functions were in conflict) and see what happens. At least now I know how to fix it if it recreates the same error.
Thanks so much you guys!