The whole reason Catherine enters Carl's mind is to learn the location of his latest victim. They still have not learned this when Catherine takes him into her head, but she goes ahead and kills him almost immediately without even asking him about this crucial information. [Vince Vaughn's character knows where the girl is, that's why he got them out of the killer's mind. He saw the symbols on the tank and knew where the girl was. Jennifer Lopez's character went back in to try to save the child.]

When Carl is in his deep coma, Catherine enters his mind in the lab-room using the special technology. However due to a "power failure," she then has to go across the room to fiddle with some circuit breakers and we assume she isn't in Carl's mind yet, however she then realizes she is already in Carl's mind - but if he has been in a coma for a few days, Carl couldn't possibly know the layout of the lab that he has been taken to, or what Catherine's colleagues look like and what they're wearing or even the red suits he and Catherine are wearing and the fact that they're suspended on wires and are wearing face-cloths, because he was in the coma before any of this happened. If Catherine is in his mind, then all this information we see in his mind isn't possible, as he could never of gathered all this information for him to even imagine it all so accurately - he would have never seen the lab room, and the red suits and Catherine's colleagues. It makes for a good, sudden twist - however it doesn't fit. [Carl had already begun to deeply effect Catherine. All he had to do was strongly suggest that she was back in the lab and HER mind filled in the rest of the details.]

Jennifer Lopez has a button on her suit which enables her to return from within somebody else's mind. It is suggested that by pressing this button in her "hallucination" she is able to press it in real life. However none of the other movements she makes in her dreams is duplicated in the physical world, or else she would never stay on the bed. [Given her mental discipline, it is likely that she has control over which movements occur in the physical world and which ones occur in the mental world.]