Ziz said:http://www.youtube.com/watch?v=PU_XlgpNTh8
4:45 - Joker: "Don't worry. I'm going to tell you where they are - both of them - and that's the point. You'll have to choose."
That's why I thought he was telling the truth about the addresses and the subsequent change was a continuity mistake. Joker was confident that Batman couldn't save both of them so no point in lying about who was where.
Just to chip-in on this one, to say how it played out to me.
As ShiftyEyes pointed out, Batman tells Gordon that he is going after Rachael....
Although the Joker knew he was going to hurt Batman with the fact that he was confident that he couldn't save BOTH people in time, and was happy to reveal both addresses to him.....he ALSO intended the additional, and probably worse kick in the teeth to him, by swapping the facts around, in case he did manage to reach the address of the one he wanted to personally rescue the most, in time.
He's a mean, and tricky fellah, that Joker.