While many coaches and players are taking it easy right now, the Mack Brown Curse is hard at work. It claimed its latest victim yesterday. Oklahoma State freshman running back Dexter Pratt was charged with possession of marijuana. The charges say Pratt and teammate Jamal Mosley "knowingly possessed and controlled within his residence a small plastic bag containing what appeared to be, and subsequently field tested positive as a small amount of marihuana (sic)." Pratt was