Fails with "Invalid secret key"

I'm using Deja Dup 8.1 on Jaunty (from the PPA). I get the above whenever I try a test backup to Amazon S3. My S3 account is active and I use it through other means so I know it is valid. I've tried a number of variations and it always comes back to the same message. Just to verify:

I set backup location to Amazon S3. Next I enter my Access Key ID from Amazon (not my Secret Key). I leave the folder as /, though I have tried using a known subfolder from the account. I chose a sample local folder with data for a test and leave exclude on Trash. I then check Encryption and close. When I select Backup it gives me a summary with the backup location "Folder / on Amazon S3." It says "preparing" then "backing up" and the first couple of file names flash across then it pops up "Backup Failed" and the message above, "Invalid Secret Key."

I've tried it with and without encryption. I have cleared the values from gconf and begun again. I even placed my existing bucket name in the gconf slot where Deja Dup was making up a new one. I've deleted the password/passphrase from the keyring and it then pops up a secondary window asking for a password along with my "username" (which is my Amazon S3 Access Key ID). I've used my Secret Key and I've used a random passphrase for encryption.

Let me know if I can try something else. I like the simplicity of this app and would like to start using it. With a couple more small features, I think it might be just the thing for basic Linux backups.

Thanks.