How long after a lease ends does the landlord have to claim damages to the property if she agreed at the move out inspection that there were no damages?

According to the Minnesota Judiciary: At the end of the tenancy, a landlord must return the tenant's security deposit or give the tenant a written explanation as to why the deposit or any part of it has not been returned,Minnesota Statute 504B. 178.   Interest on the security deposit is calculated as simple noncompound interest per year.  The interest rate is 3% per year until August 1, 2003 and 1% per year thereafter. If the landlord does not return the security deposit in the time allowed, the landlord must pay the tenant an amount equal to two times the amount of the deposit wrongfully withheld, plus interest. Minnesota law allows a landlord to withhold from a security deposit only the amount necessry for unpaid rent, damages to the rental unit beyond ordinary wear and tear, or other money owed to the landlord under an agreement, Minnesota Statute 504B.178 subd. 3(b)(1). The landlord must make the refund within 21 days after the day the tenancy ends. The tenant must give the landlord a forwarding address.  You may have to sue and the witnesses will be crucial.  Good luck.