I hear the frustration. We are all different and our bodies react differently to the changes that occur.
One thing that is suggested is that you don't start exercise (if you hadn't been exercising before) for at least 3 weeks. If you had been exercising before, then cut it in half. That gives your body time to adjust to the changes.
Since the timing of the medimeals seems okay, and the water intake seems okay, I would say there might be issues with salt/water retention from the protein in the L&G (less probable), the bar being to caloric, or the time between your last medimeal of one day and your first the next.
Many times the reason that we don't lose is simply that our bodies go into starvation mode and hold onto everything. In this, whatever we eat our bodies convert to glycogen and keep it for later as fat. I know it goes against every concept you know about losing weight, but we sometimes need to feed our bodies to lose. Especially since you have been exercising during the first 3 weeks.
I would suggest either cutting out the walking, replacing the bar with a different medimeal, or having an extra medimeal after your walking. See if that helps and go from there.