I don't have too much to add about why but I also get in that zone of misery. I do well low carb or much higher. The in between doesn't work for me.
I have been on and off Primal lately due to some stress but I think reading this thread and seeing that others have the same experience I need go back to low carb to get fully back into the swing of things. I don't even have to go that low carb. I can handle 75g a day and sometimes a bit more but once I go over 100g it doesn't work.
Pre-Primal SW: 161