Physically Incorrect

Here’s a puzzle I got asked over on physicsforums. My solution was intuitive, but later on a different forum member presented a much more concise and general approach, so there are at least two ways of solving this one. Here goes.

A party is thrown. Here’s what you know about it:

1. Every person at the party knows precisely 22 other people.
2. Now, pick two people, call them A and B. If A knows B, then they have no mutual friends.
3. If A doesn’t know B, they have precisely 6 mutual friends.

How many people are at the party?

EDITED, 27/June/2009: a solution has been posted here.