Help: Unable to Enable Result Cache

Environment:

Oracle 11.2.0.2 on RH Linux 64
memory_target = 4000 MB

Memory Advisor in DB Control shows the following:

Automatic Shared Memory Management Enabled
Total SGA Size (MB)2608
Shared Pool 1536
Buffer Cache 960
Large Pool 32
Java Pool 16
Other 64

 I have two DBs in the same Oracle home. I was able to enable result in one of them, but not the other. Here was what did:

alter system set result_cache_max_size = 32M scope=both;  -- System altered

select * from v$parameter where name = 'result_cache_max_size';  --- 32M

exec DBMS_RESULT_CACHE.BYPASS(FALSE);

SELECT DBMS_RESULT_CACHE.STATUS FROM DUAL; -- disabled