subselect results in poor performance

Hi all,
Running query with partition pruning information in subselect but optimizer does not choose for partition pruning making query slow. If subselect is replaced with literal/string (which is result of subselect), query is fast.
Have tried many hints...without success. Anyone else an idea ? note : query below is part of big sql.

1. no partition pruning on MV_RRP00010 => SLOW makes use of subselect (string in comment)

select VW_RRP00010.*,RRP0.TB_RRP00115.*
FROM RRP0.MV_RRP00010 VW_RRP00010,rrp0.TB_RRP00115 where VW_RRP00010.LOAD_DT = TB_RRP00115.LOAD_DT AND VW_RRP00010.LOAD_TYPE_CD = TB_RRP00115.LOAD_TYPE_CD AND VW_RRP00010.FUSE_CTY_ID = TB_RRP00115.FUSE_CTY_ID AND (VW_RRP00010.ISO2_CTY_CD = TB_RRP00115.ISO2_CTY_CD OR ' ' = TB_RRP00115.ISO2_CTY_CD)
and tb_rrp00115.load_dt = (SELECT TB_RRP00104.LOAD_DT COL1 FROM RRP0.TB_RRP00104 TB_RRP00104 WHERE '1' = TB_RRP00104.VSN_CD AND 'D' = TB_RRP00104.LOAD_TYPE_CD)
/* and tb_rrp00115.load_dt = '14/01/2007' */

Operation Object Name Rows Bytes Cost Object Node In/Out PStart PStop

SELECT STATEMENT Optimizer Mode=CHOOSE 64 K 2891 HASH JOIN 64 K 10 M 2891
PARTITION RANGE SINGLE KEY KEY
TABLE ACCESS FULL RRP0.TB_RRP00115 48 K 6 M 1290 KEY KEY PARTITION RANGE ALL 1 35
TABLE ACCESS FULL RRP0.TB_RRP00104 1 12 4 1 35 PARTITION RANGE ALL 1 35
TABLE ACCESS FULL RRP0.MV_RRP00010 1 M 33 M 754 1 35 2. partition pruning on MV_RRP00010 => FAST subselect in comment, makes use of string

select VW_RRP00010.*,RRP0.TB_RRP00115.*
FROM RRP0.MV_RRP00010 VW_RRP00010,rrp0.TB_RRP00115 where VW_RRP00010.LOAD_DT = TB_RRP00115.LOAD_DT AND VW_RRP00010.LOAD_TYPE_CD = TB_RRP00115.LOAD_TYPE_CD AND VW_RRP00010.FUSE_CTY_ID = TB_RRP00115.FUSE_CTY_ID AND (VW_RRP00010.ISO2_CTY_CD = TB_RRP00115.ISO2_CTY_CD OR ' ' = TB_RRP00115.ISO2_CTY_CD)
/* and tb_rrp00115.load_dt = (SELECT TB_RRP00104.LOAD_DT COL1 FROM
RRP0.TB_RRP00104 TB_RRP00104 WHERE '1' = TB_RRP00104.VSN_CD AND 'D' = TB_RRP00104.LOAD_TYPE_CD) */
and tb_rrp00115.load_dt = '14/01/2007'

Operation Object Name Rows Bytes Cost Object Node In/Out PStart PStop

SELECT STATEMENT Optimizer Mode=CHOOSE 63 K 2851 HASH JOIN 63 K 10 M 2851
PARTITION RANGE SINGLE KEY KEY
TABLE ACCESS FULL RRP0.MV_RRP00010 91 K 2 M 1389 KEY KEY PARTITION RANGE SINGLE KEY KEY
TABLE ACCESS FULL RRP0.TB_RRP00115 48 K 6 M 1290 KEY KEY Received on Tue Jan 16 2007 - 09:11:30 CST