I read a comment from Dr. Eades on this kind of situation (don't have time to find the link). He suggested potassium might be the issue.
Updated: Okay, here's the post. In response to a comment, he writes:
"Being in chronic ketosis does not necessarily make one tired. Usually tiredness in the face of ketosis comes from a potassium deficiency. People go into ketosis because they are cutting carbs, cutting carbs reduces insulin levels, reduced insulin levels encourage the kidneys to get rid of excess fluid. As this excess fluid leaves the body it carries potassium along with it, often causing a potassium deficiency. Replacing the potassium usually solves the problem."