NJ Security Deposit and Pets

I recently moved out of my apt complex on July 23rd 2008. My landlord has
kept my entire security deposit and wants more due to damages casued by
pets.
Story:
I moved into the complex 4 yrs ago when pets were allowed by a different
Company/Landlord. The new landlord for the last 2 yrs grandfathered my pets
in. I did switch apts and signed a new lease but they still allowed me to
keep my pets (entire SD was returned) Now that I finally left the complex
they are saying that the pets detroyed the carpet and they needed to replace
the entire subfloor and I am responsible because I had the pets. Can they
change the rules like that? I don\'t understand why they would return my
full deposit from the previous apt and now keep all of it if I had the same
pets?

also to note: The previous tenants that lived in my apt had a dog and the
subfloor has been in place since the 70\'s when the building was
constructed. These tenants were not charged for the carpet but it was
completely replaced before I moved in.

No rule was changed. You were allowed to keep your pets. But just beacuse you were allowed to have the pets doesn't mean you aren't responsible for the damages they cause. If your pets ruined any flooring, you need to pay the depreciated value of the flooring. Since the carpet was new at move in, you owe the current value of the carpet in that unit as determined by their depreciation schedule on their taxes. The value of the subflooring would be determined in the same manner. You have to pay for any pet damages if you own pets.