I have seen this with git master head:
$ pg_dump test
:
:
:
COPY insert_lock (reloid) FROM stdin;
pg_dump: [archiver] internal error -- WriteData cannot be called outside the context of a DataDumper routine
--
Tatsuo Ishii
SRA OSS, Inc. Japan
English: http://www.sraoss.co.jp/index_en.php
Japanese: http://www.sraoss.co.jp