9.1.3: launching streaming replication

i have a server in the ec2 cloud which in theory is set up as a master; it starts and runs. i've got an amazon s3 bucket mounted using s3fs on both the master and the standby (the standby is also set up in the ec2 cloud.)

i followed the steps here: http://wiki.postgresql.org/wiki/Streaming_Replication
and have the backup and the wal archive on the s3 bucket and they are both there.

when i go to start the hot standby, i pretty consistently get

LOG: entering standby mode
cp: cannot stat `/db-backup/wal_archive/000000010000000000000001': No such file or directory
WARNING: WAL was generated with wal_level=minimal, data may be missing
HINT: This happens if you temporarily set wal_level=minimal without taking a new base backup.
FATAL: hot standby is not possible because wal_level was not set to "hot_standby" on the master server
HINT: Either set wal_level to "hot_standby" on the master, or turn off hot_standby here.
LOG: startup process (PID 29938) exited with exit code 1
LOG: aborting startup due to startup process failure

and the startup of the hot standby fails. the Riggs admin cookbook says "you will need a short delay", but has no guesstimate on the length required. i don't even know if i'm seeing this problem or something else.

if i need to run a new backup, what cleanup do i need to do of old backups and wal_archives? could this be interfering with the startup of the standby? i've gone through several iterations and fixed some problems, and wonder if there's obsolete data that is messing things up?

thanks,
richard