Marco,

In order to understand what really happens, you might want to update row by row, like in the following construct:

llToast = .F.
lnNext = GETNEXTMODIFIED(0)

BEGIN TRANSACTION
DO WHILE lnNext # 0
  GO (lnNext)
  IF ! TABLEUPDATE()
    llToast = .T.
    EXIT
  ENDIF
  lnNext = GETNEXTMODIFIED(lnNext)
ENDDO

IF llToast
  ROLLBACK
  TABLEREVERT(.T.)
  ErrorMsg(this.cMsgUpdateFailed )
  RETURN .F.
ELSE
  END TRANSACTION
ENDIF

José