A woman has a close male friend.
This means he is probably interested in her, which is why he hangs around her. She sees him strictly as a friend. This always starts out when she says, "You're a great guy, but I don't like you in that way."
This is the equivalent of the guy who goes to a job interview and the personnel manager tells him:
"You have all the qualifications we are looking for, but we're not going to hire you. We will, however, use your resume as the basis for comparison for all other applicants. We're going to hire somebody who is far less qualified and is probably an alcoholic. And if he doesn't work out, we'll hire somebody else. But we still won't hire you. In fact, we will never hire you. But we will call you from time to time to complain about the person that we hired."
And this one reason why platonic relations between men and women rarely work.
(Reworded from a joke found at the qdb site c/o bash.org)