FormatMessage() (This should have been in 8.2.0, patched to 8.2.X and
HEAD):

I think this problem to be complex....
http://archives.postgresql.org/pgsql-hackers/2006-11/msg00042.php

FormatMessage of windows cannot consider the encoding of the database.
However, I should try the solution now. It is necessary to clear the
problem.

Multi character-code exists together in message and log. It doesn't
consider
the data base encoding that the user intended....

The user in multi-byte country can try this.
http://inet.winpg.jp/~saito/pg_bug/MessageCheck.c

That is, it is likely to become it in this manner.(Japanese)
http://inet.winpg.jp/~saito/pg_bug/FormatMessage998.png

Hiroshi Saito