libpq, PQExecParams and the inserting of binary data

I have been trying to figure this out all morning, and I've gotten no
where so far.

I am trying to insert binary data into a bytea column with
PQExecParams.  I couldn't find any documentation on using PQExecParams
with binary parameters, do I tried to do it this way:

int _ma_logbody(struct MailData *MailData, char *bodyp, size_t bodylen)   {   const char *paramValues[2];   char
*text_body;  PGresult   *res;   size_t      newlen; 
   text_body = PQescapeBytea(bodyp, bodylen, &newlen);
   paramValues[0] = MailData->MsgId;   paramValues[1] = text_body;
   res = PQexecParams(conn, "insert into ma_body (msg_id, body)
VALUES ($1, $2);",           2,       /* params */           NULL,    /* let the backend deduce param type */
paramValues,          NULL,    /* don't need param lengths since text */           NULL,    /* default to all text
params*/           0); 
   PQfreemem(text_body);
   if (PQresultStatus(res) != PGRES_COMMAND_OK)       {       log(LOG_MAIL, "Postresql insert failed: %s",
PQerrorMessage(conn));      log(LOG_MAIL, "bodylen: %d, bodyp: %s", bodylen, bodyp);       PQclear(res);
PQfinish(conn);      conn = NULL;       return(0);       } 
   PQclear(res);
   return(TRUE);   }

As you can see, I assumed I could use PQexapeBytea to escape the
binary data and then just use the returned value as a text parameter.
However,  I randomly get insert errors with the error message:
"invalid input syntax for type Bytea".

If anybody could help me find the right way to do this I'd really
apreciate it...