AMEX points transfer to FC problem

OK, in brief: My OH has an AMEX and we want to transfer points to his FC account so we can secure reward seats this week. However, his old FC number is on the account as the last time we did this was probably before the introduction of the new numbers. He tried to add a new account number and the website for the last few days just gives us the message "this action cannot be performed at this time, sorry for the inconvenience." Are the old account numbers still linked to the current ones? We need to make a fairly substantial transfer so we don't want the points disappearing into the ether! I'm also wondering if he can edit the old account number somehow.
Thanks
Thanks
