See thread:
http://s3sync.net/forum/index.php?topic=100.0If specifying AWS_CALLING_FORMAT: SUBDOMAIN in s3config.yml, s3sync/s3cmd fails. It says 403 Forbidden (SignatureDoesNotMatch)
If I specify it on the command line (AWS_CALLING_FORMAT=SUBDOMAIN ./s3cmd.rb createbucket mybucket EU) it works. Unless it is also specified in the yml file, in which case it fails.