Why don't you have access to your old address any more? Did you remove the account wallet that had that address?

Did you keep the private key to that address somewhere? Did you export it from the website? You should always backup your keys in case something like this ever happens again. The old keys, if they are backed up, will allow you to easily restore access to those coins.

If you did not store those keys anywhere, and you shut down the online wallet (which effectively destroyed it), I'm afraid those coins are gone for good.

It may be worth noting that this isn't the first time (and sadly won't be the last) something like this has happened.