by Mike Krumboltz Ruthless assassins, or a very pregnant woman? Neither should be messed with, and both are featured in movies opening at theaters this weekend. Romantic comedy " The Back-up Plan " stars Jennifer Lopez as a woman who gets artificially inseminated, and meets her dream fella soon after. " The Losers " is an action flick about a group of rogue assassins out to get revenge on the politicians who done them wrong. Can either film hold its head high with the critics?