Trying out replication: cp cannot stat log file during recovery

Greets,

Pg 9.0.3.

I'm trying out Pg's built-in replication for the first time and noticed
something odd.

On the slave I see the following in the logs (after rsyncing all from master
to slave and firing up Pg on the slave):

...
restored log file "000000010000018E0000000E" from archive
restored log file "000000010000018E0000000F" from archive
consistent recovery state reached at 18E/10000000
restored log file "000000010000018E00000010" from archive
cp: cannot stat `/home/arc/000000010000018E00000011': No such file or directory
unexpected pageaddr 18D/91000000 in log file 398, segment 17, offset 0
cp: cannot stat `/home/arc/000000010000018E00000011': No such file or directory
streaming replication successfully connected to primary
...

/home/arc is an NFS mount from master and is where the WAL archive is kept
(yes, I'll move it eventually; for now I'm just testing).

Things seem to run fine up until (and after) log file
000000010000018E00000011. That particular file is definitely present. Why
would cp(1) fail to stat the file when it worked fine for all the others?

I notice from another mailing list post that 'unexpected pageaddr' is possibly
not that serious and is probably unrelated to the cp/stat error above.

However, since recovery seems to have skipped a log file, what would that mean
in terms of the slave being a true copy of master and integrity of the data?

thanks
Henry