A: Too stale to use after a year? Bull-pshaw. A decade, maybe. Fill your Rolodex with anyone who can vouch for your skills and character. Just make sure you call the people first to remind them who you are, and make sure their offer still stands.
If any of those "risky" references try to shiv you somehow, your collection of positive reviews should make clear that the problem is with the naysayers, not you.
(Er . . . it is them and not you, right? Either way, you might want to come up with a non-defensive defense, in case an interviewer hears something negative from a detractor and asks you about it.)
Karla L. Miller writes an advice column on navigating the modern workplace. Each week she will answer one or two questions from readers. Miller has written for and edited tax publications for 16 years, most recently for the accounting firm KPMG's Washington National Tax office.