sqlerrd[0] <> 0 What does it mean?

Hello! I would like to know the meaning of the sqlca.sqlerrd[0] field in Informix Online 5.0. Background: Mode ANSI database, ESQL/C. I have $PREPAREd a "SELECT ... WHERE col = ?" statement, $ALLOCATEd a descriptor etc. Then, I $OPEN a cursor, which returns SQLCODE = 0 and sqlerrd[0] = 3, which is normally 0. I wouldn't mind sqlerrd[0] = 3 very much, but the $DESCRIBE that follows the OPEN statement dies with a segmentation fault, which doesn't happen when sqlerrd[0] is 0. The really strange thing is that is doesn't happen always. It depends on the value I set for the "?" in the SELECT statement. (I use a $SET DESCRIPTOR statement to do that.) Since the nonzero contents of sqlerrd[0] is the only thing (for me to see) that is different, I hope that it gives some insight as to what is going wrong. Ideas anyone? -Walter