From Engadget:
The latest Gingerbread update is now rolling out over-the-air. Unfortunately, the update also broke Google Voice on our N1 — something that we fixed by downloading and installing an old GV.apk and then updating to the latest version in Market per the instructions left by our peers struggling with the same issue over at the Google support forum.
These are the kinds of little things that hurt Android from being loved by the mass market consumer.