Found something that worked, finally!
http://answers.ea.com/t5/Mass-Effect-3/Mass-effect-3-crashes-on-startup-PC/td-p/249230
Short answer- disable Origin. Quoting the thread,
"The only way I have been able to avoid it is to disable Origin in-game. Open Origin on your PC, go to the upper left where it says "Origin" and click. A menu should pop down, and somewhere in this menu you should see an "Application Settings" option. Click on this option, after which a new window called "Settings" will show up. Click on the "IN GAME" tab in this window, and then uncheck "Enable Origin In Game." Then go ahead and click "DONE" near the bottom right.
I hope this helps. If not, then I do not know what else to suggest. Just some advice for this temporary fix: when Origin is disabled in-game, you cannot access the origin menu in-game, and therefore cannot respond or check text messages from friends (or almost every other Origin feature) until you exit the ME3 game (assuming that you are playing ME3 in fullscreen mode rather than window mode)."
