BUG #5164: COPY command: invalid byte sequence 0x80

The following bug has been logged online:

Bug reference: 5164
Logged by: Bogdan Mihaila
Email address: bm2004mvc(at)yahoo(dot)com
PostgreSQL version: 8.1 and 8.3
Operating system: Linux
Description: COPY command: invalid byte sequence 0x80
Details:

Hello!

I searched the internet for this problem, but I didn't find an answer.
Please help me.

I make a COPY TO command (in a 8.1 version, under Linux) for a table that
contains text in the UTF-8 encoding. The command is:

set client_encoding = 'utf8';
DROP TABLE "acte1";
CREATE TEMP TABLE "acte1" AS
SELECT * FROM "Oficiale"."acte" WHERE id = 57502;
COPY "acte1" TO '/home/bogdanm/eugen.copy';

Then I make a COPY FROM (in a 8.3 version,under the same Linux machine as
above) like this:

set client_encoding = 'utf8';
copy "Oficiale"."acte" from '/home/bogdanm/eugen.copy'

It works!

But, where I specify the interval like this:

WHERE id > 57500 and id < 57600;

it doesn't work, saying:

ERROR: invalid byte sequence for encoding "UTF8": 0x80
HINT: This error can also happen if the byte sequence does not match the
encoding expected by the server, which is controlled by "client_encoding".
CONTEXT: COPY acte, line 51

Why is that? The second range obviously contains the first...

Thanks very much in advance,
Bogdan