The Microsoft Oracle OLE DB provider does not currently support random Access to BLOB data with server-side cursors - the BLOB column must appear to the end of the SELECT clause.

ms-help://MS.MSDNQTR.2005JAN.1033/enu_kbadobj/adobj/194975.htm
ms-help://MS.MSDNQTR.2005JAN.1033/enu_kbadobj/adobj/185958.htm