Comment by cperciva

S3 is currently (22:00 UTC) back up.

The timeline, as observed by Tarsnap:

    First InternalError response from S3: 17:37:29
    Last successful request: 17:37:32
    S3 switches from 100% InternalError responses to 503 responses: 17:37:56
    S3 switches from 503 responses back to InternalError responses: 20:34:36
    First successful request: 20:35:50
    Most GET requests succeeding: ~21:03
    Most PUT requests succeeding: ~21:52