本家のフォーラム
Thread: ec2-bundle-vol fails
にも上がっていますが、EC2のイメージを作成する時にrsync関連の
警告が出ることがあるようです。

NOTE: rsync with preservation of extended file attributes failed. Retrying rsync
without attempting to preserve extended file attributes...
NOTE: rsync seemed successful but exited with error code 23. This probably means
that your version of rsync was built against a kernel with HAVE_LUTIMES defined,
although the current kernel was not built with this option enabled. The bundling
process will thus ignore the error and continue bundling. If bundling completes
successfully, your image should be perfectly usable. We, however, recommend that
you install a version of rsync that handles this situation more elegantly.

警告は出るものの、イメージ自体は作成されている模様。