[rabbitmq-discuss] error: {amqp_error, precondition_failed, "unknown delivery tag 29", 'basic.ack'}

[fbjork]

When we push our Ruby app to production, after processing a few
messages we get this in the RabbitMQ (2.4.1) error log:

=ERROR REPORT==== 14-Jul-2011::22:31:30 ===
connection <0.29022.1855>, channel 1 - error:
{amqp_error,precondition_failed,"unknown delivery tag 29",'basic.ack'}


Any idea what it means who to fix it?