As of April 21, 2014, you will no longer be able to retrieve the existing secret access key(s) for your AWS (root) account.
If you have become dependent on this feature, you should download your key from the legacy security credentials page now and then save it in a safe and secure location. Better yet, follow our best practices and create an IAM user with access keys. The legacy security credential page will warn you about the upcoming change:
PS - I don't want anyone this change to take anyone by suprise! Please consider sharing it with your colleagues and your friends.