The shakes don't contain the sugar alcohols you find in the bars, so they shouldn't cause a stall. In fact, many people (myself included) find they increase weight loss when replacing a meal. I have 1 daily for breakfast. Remember a stall is 3-4 weeks without losing weight or inches, so a week is far from a stall. No matter what you do there will be times where you don't lose for a week, especially as you get closer to goal. So try to be patient & just stick with it. Good luck.
God Bless,
Amy-Lynne