Don't think anyones noticed this... **SPOILERS**

Rating: 9/10 (4 June 2001)

SPOILERS!!!!!

I think there is a definite clue at the end of the film to explain that Lennys' condition is psychological and not physical (i.e. he chooses to have short memory)...
At the end of the film when he decides to make Teddy the John G. he's looking for, he takes a piece of card and writes 'FACT 7: License Plate Number xxxx'
How did he know he was up to fact number 7? He could have been on fact number 3 for all he could remember!
Maybe it was a mistake, but I like to think it reinforces that Lennys problems are of his own doing not because of the head injury.