Game officials will be permitted to use instant replay at any point during a game to determine (i) whether a successful field goal was correctly scored as a 2-point or 3-point field goal, and (ii) whether, for purposes of awarding the correct number of free throws, an unsuccessful field goal attempt on which the shooter was fouled was a 2-point or 3-point attempt.
Read more here...
http://www.nba.com/2008/news/10/23/102108videoreplayrules/index.html
I really hope this isn't used excessively, it could really ruin the pace of a game and a team's momentum.