Really???

I think you will I've been there million gazillion times and finally I have succeeded!

There are many, many things that can influence the result! If you are having the calories and nutrition that you need, having some exercise that maybe just postpone your weigh inn day. I was quite upset last weekend, because I thought that my weight is stuck in again (and actually more again), but 3 days passed and I am where I expected my self to be.
I went out to have some food and drinks with my friend and didn't really follow nutrients and I am pretty much sure that that was the reason.
Chin up!

Have you recently started a new exercise program? That can cause temporary fluid retention. Muscles retain fluid for repair
Are you logging all your foods with accurate database entries? There are many false entries out there. Make sure you match the database entries with the nutrition information on your food packaging. Don't use generic entries. If you have to, create your own. Use the recipe builder, too.
Do you use a food scale and weigh all solid and semi solid food in grams? Weighing food on the scale ensures accuracy. It's very easy to overestimate food calories. Whenever I weigh my food and am honest with logging, I lose weight. Also, don't get upset if you go over your calories sometimes...it's not worth it. Remember the overall progress, not temporary screw- ups (we're human after all!
Do you log exercise in MFP? MFP greatly overestimates exercise burned calories. You can eat a portion of those back (around 50% is fine).
How long have you been doing this? If it has been less than 6 weeks, keep going! Weight loss isn't linear. Don't get upset over gains...ever. Gaining, losing and maintaining are part of the normal overall weight loss trend
How much sodium do you consume? Too much sodium can cause fluid retention that masks weight loss. Fluid retention and fat gain are different. Muscle takes a very very long time to build, too.
If female (and if this applies), are you near that time of the month? Before and during TOM and ovulation, I tend to gain at least 6lbs, but it comes right off after. No biggie
What are your expectations? Expecting to lose say, 5lbs a week every week is incredibly unrealistic. Instead, stick to a 2lbs per week loss (if you have over 50lbs to lose), 1.5 loss (from 30-50), 1lb per week (20-30), .5lbs per week (30 and under).

Also, there are no bad foods, there are no bad times to eat, fat and carbs aren't bad, and diet pills and silly diets are useless.