problem about message type 0x45

I am using the posgresql 6.5.1.

I have begin a transaction and insert a lot of tuples in the
transaction. The simplified code is as following:

----------------------------------
res = PQexec(conn,"BEGIN");
PQclear(res);

PQexec(conn, "INSERT INTO qms_table (idr1, idr2, sequence) VALUES ('chu1', 'wind1', 0)" );
PQclear(res);

PQexec(conn, "INSERT INTO qms_table (idr1, idr2, sequence) VALUES ('chu1', 'wind1', 1)" );
PQclear(res);

....

res = PQexec(conn,"END");
PQclear(res);
-------------------------------

But I got a message as:

Backend message type 0x45 arrived while idle

When inserting the third or forth tuples, and the backend process exits.

Does anybody know what the message type 0x45 means? What document can I find
the related information? And does any body know what may be the reason casued the
problem?
Thanks