The apk must be signed with at least one certificate in common with the previous version

I get this error when I attempt to publish an update to an app on the market. I'm using the same keystore and the same key as the previous update I published. I've no idea what to do. There are no errors or issues when signing or z开发者_运维问答ipaligning.

I've only ever had 2 keystores and 2 keys on this computer. I've tried one, then the other, and both at once. The market never accepts it as being signed with same key.

Help!