Crank bolts do need to be very tight to let the reverse thread work for you. I'm sure maddslacker can come up with a touque setting. I would say that you may have a bottom bracket/bolt issue if it "just came loose". Remember advise is free and you get what you pay for.
Fat Billy sponsored by: Any all you can eat buffett, Michelin, Panaracer, Shimano, Serotta Bicycles, Sidi shoes, Bell Helmets, Monkey light Handlebars, Camel Back products. Wait a minute I give them money and all they give me is high prices. Never mind! Too wet to ride? Try Planking to help keep muscle tone.