I make chocolate chip cookies from Pamela's Baking mix about every other week, and have never had that problem. I always use real butter instead of margarine, and I usually throw in a tablespoon or so of almond meal. Butter, egg and vanilla are the only liquids. Maybe used too much mix?
I am embarrassed to post this but I misread the 1/2 cup butter to be 1/4 cup. My, are they dry . I'd blame it on my son who was helping me, but I took the butter out hours earlier on my own to soften. Well, duh.