HELP !!! - Subselect problem

Hi, i try to run

Select F.Id,
(select Sum(RIWTE_FattRec.Prezzo * RIWTE_FattRec.Quantita)
FROM RIWTE_FattRec WHERE RIWTE_FattRec.IdFattura = F.Id ) as totale
from RIWTE_Fatture F


I receive this error
****************************************************
ODBC Error: SQLSTATE = 37000, Native error code = 0
Syntax Error: Select F.Id,
 (select<< ??? >> Sum(RIWTE_FattRec.Prezzo * RIWTE_FattRec.Quantita)
 FROM RIWTE_FattRec WHERE RIWTE_FattRec.IdFattura = F.Id ) as totale
 from RIWTE_Fatture F

Releases:
Pervasive Sql 8.50
Pervasive Control Center 8.50.189.000

Thanks to all.

Alessandro Zambonin