If you are sure you didn't copy the wrong address after generating the new address, you should send a support ticket to blockchain.info, or send a PM to piuk (https://bitcointalksearch.org/user/piuk-17928).
There have been situations in the past where people have sent bitcoins to an address right after generating it in their blockchain.info wallet without making sure that the address has synced up with the blockchain.info servers. Then they close their browser and discover later that the address (and private key) are gone from their wallet (since it is stored only in the browser until it is synced to the blockchain.info servers).
I'd suggest that you be very careful and NOT use that computer (or at least that browser), until you've gotten some assistance from Piuk here at bitcointalk, or directly from blockchain.info support. It is quite possible that the private key and address are still stored in a browser cache file somewhere. Hopefully either Piuk or blockchain.info can help you find the necessary information in the cache.
If the private key is no longer in your cache, then you can pretty much figure that the bitcoins are permanently gone.
This could definetly be the case. Hope you ill gt your coins man.