See post #61.
It comes down to a determination as to what the term "eligible" or "eligibility" means. Does it mean "capacity to be elected" as posited by Eugene Volokh (entry of 3/8/2004 03:23:40 PM)? Or is there a distinction between the terms "election" and "service"? See Bruce G. Peabody, Scott E. Gant, Twice and Future President: Constitutional Interstices and the Twenty-second Amendment, 83 Minn. L. Rev. 565(1999).
As I stated before, I think it is an open question, and not one where it can be stated as a flat assertion that it would violate the Twenty-Second Amendment (as incorporated into the Twelfth Amendment) for a formerly twice-elected President to serve as Vice-President.