Regarding domain keys configuration for my e-mail

Regarding domain keys configuration for my e-mail

I set up domain keys configuration some time ago, but I forgot to change the domain record (delete t=y), so the domain key authentication did not work for some time. Now, I login into my account, I try to generate a new key, but I get a "Database operation failure" message. How can I delete the old record, so I can begin working on a new one?