OCILobArrayRead() reads odd result from CLOB fields in 11.2.0.1.

My problem is:
OS: Windows 7 SP1 64bit
Oracle: Server 11.2.0.1.0 language, territory and character set: AMERICAN_AMERICA.AL32UTF8 (NCharset: AL16UTF16)
        Client 11.2.0.1.0 language, territory and character set: AMERICAN_AMERICA.AL32UTF8 (NCharset: UTF16)
        (For OCI client environment setup, we callOCIEnvNlsCreate( envhp, OCI_THREADED, NULL, NULL, NULL, NULL, 0, NULL, 873, OCI_UTF16ID );)
        
We have a table SUPPORTTESTM1, the table definition as follow:
RECORD_KEY    INTEGER                
ID            FLOAT                
F1            CLOB                
F2            CLOB                
F3            CLOB

There are 3 rows in the tables as follow:
RECORD_KEY  ID  F1      F2      F3
748620186    1    a        bb        cc
-360314469    2    a        b        cc
279120284    3    aa        b        cc

Our system calls OCILobArrayRead() to read all the 3 CLOB fields for one record.