Have you taken your measurements? Since muscle weighs more than fat, if you are exercising you may be gaining muscle. Maybe take your measurements once a month and see if you see any difference in the inches instead of watching the scale. I agree with others here. It will work if you stick to it. Sometimes (most of the time) it doesn't happen as fast as we think it should, but it will.
Starting weight 2/22/12: 275
Goal weight: 140ish