Some problem with warm standby server

Hi,
I have some doubts regarding the settings and the access procedure of
warm standby servers:
- can autovacuum be safely enabled on the replicator?
- I'm using pg_standby (from cvs) that is generally working well as
expected (logs are copied with
scp); today I wanted to temporarily stop the replication to verify
some data to restart it later on, so
I touched the trigger file, waited for the log to report "database
ready", verified that the
databases were actually up-to-date. All was fine, then I ran

rm -f pg_xlog/* pg_xlog/archive_status/*
mv recovery.done recovery.conf (the permissions were right)
/etc/init.d/postgresql stop ; /etc/init.d/postgresql start

the replication seemed to start:
----
---------------------------------------------------
LOG: database system was shut down at 2007-04-27 12:16:13 CEST
LOG: starting archive recovery
LOG: restore_command = "/usr/local/bin/pg_standby -s 5 -w 0 -t
/usr/local/postgres_replica/trigger /usr/local/postgres_replica/log/ %f %p"
cp: cannot stat `/usr/local/postgres_replica/log//00000001.history': No
such file or directory
cp: cannot stat `/usr/local/postgres_replica/log//00000001.history': No
such file or directory
cp: cannot stat `/usr/local/postgres_replica/log//00000001.history': No
such file or directory

then I updated the master with a batch of inserts, but after a while the
slave stopped with
these messages:

LOG: restored log file "000000010000000000000021" from archive
LOG: record with zero length at 0/21000048
LOG: invalid primary checkpoint record
LOG: restored log file "000000010000000000000020" from archive
LOG: restored log file "000000010000000000000021" from archive
LOG: invalid resource manager ID in secondary checkpoint record
PANIC: could not locate a valid checkpoint record
LOG: startup process (PID 19619) was terminated by signal 6
LOG: aborting startup due to startup process failure

What did I do wrong? Is there any other procedure to follow to restart a
stopped replication?
Thanks,
Nico