I'm experiencing maddening problems in getting WordPress to generate a new nonce for subsequent Ajax requests to process a specific action. I've tried setting the nonce_life to something reasonably short, but that has caused other problems. I've tried creating a new nonce for the callback function with a unique timestamp or something similar, but then the value of the nonce can't be compared against its name in the subsequent request.
At this stage I don't know what to do. None of the suggestions I've read elsewhere from other folks are working-- implementing those suggestions results in WordPress continuing to spit out a nonce that was the same as before.