From the New York Times:
For four years, Donaghy bet on N.B.A. games, including some that he officiated. For at least five months — starting in December 2006 — he advised professional gamblers about which teams to pick, through telephone calls and coded language. And he violated one of the primary tenets for referees by providing the gamblers with information about referee assignments, relationships between referees and players and the health of players.
You can read the rest of the story and get a reminder of everything that Tim Donaghy did here.
Donaghy explained, "I was hanging out with the wrong people,playing big-money golf matches, limos running to the casino in Atlantic City. I just started to cross a line that I shouldn't have been near as an NBA referee."
You can catch the entire interview and get a scoop on the new movie 'Inside Game'