(I live in Canada by the way, I realize this is more a US States forum. However I figure the laws regarding this scenario can't be too different.

I was in a year lease starting august 2008, however mid September I had to move out. I talked with my landlord and I told him I had another person willing to take my place at the apartment the day I left.

He said okay and that if the person is able to rent the apartment by his standards, everything would be fine and we'd get what we paid for our damage deposit back.

The new tenant cleared all the checks and moved in on sunday sept. 28/08. (The day after I moved out)
We only paid half our damage deposit because we had made an agreement with our landlord to pay the rest middle of september and before I paid it I found out that I had to move.

Now even though my landlord said if the tenant is okay and able to move in he'd give us back the deposit, he is now saying since we only paid half of the damage deposit he is entitled to keeping it.

(He also hasn't given any written notice on why he isn't giving it back. As of yet. There's also no damages either.)

So in short my question is:
Can the landlord keep the half of the damage deposit?

Thanks in advance