I have a question....e-mail me please

Rating: Null/10 (23 January 2002)

After viewing A Beautiful Mind and discussing it with others there is one part of the plot that confusses me.
***SPOILERS********
During the scene where Nash drops one of the envelopes off and is picked up by Ed Harris because they are being followed I am confussed as to the actual events that occured. It seems to me that every time Nash thought he was doing something for Harris he actually did it but the scenery in which he was doing it was different or the people he was interacting with weren't there (empty warehouses, talking to noone). In the car chase scene can anyone explain to me what really occured. The only thing that I can imagine is that he imagined the whole thing which isn't really inline with the rest of the movie. I don't think he drove a car there so it wasn't as if he was driving. I really didn't understand this part of the movie and if anyone has an idea of what I'm missing I'd appreciate an e-mail.
Thanks