E.g., did they tell you the shipping date after you placed the order, or before? If it was afterward, then it can't have invalidated the contract... you agreed to it without knowing when it would ship. If they told you before, then was it before they knew your shipping address, or after? If it was beforehand, then again, it should've been clear that they wouldn't be able to guarantee it without knowing the address. If it was after they got the address but before you placed the order, then that makes for a strong case, since it was specific to your order and what you agreed to before placing it.
