debug a mess

I am trying to figure out where the "NOTICE: current transaction is aborted,
queries ignored until end of transaction block" comes from in my code.
Basically, this is what it does:

CString strQuery
= "SELECT datname FROM pg_database WHERE name = 'mydatabase'";

if (NULL == (res = PQexec(pgconn, (CSTR) strQuery)))
{
ErrorQuit(PQerrorMessage(pgconn));
}

It is really very simple code, but each time I try to run it, the postgresql
backend gives me the "transaction aborted" error message. I checked the
mailing list archive, and Tom once explained that the reason for this error
message is the backend had quitted for some reason. Is there anyway to see
why the backend aborted the transaction?? It could be really helpful.

Thanks

Wei