use update_clients to upgrade clients to 7.5.0.3 but failed

hi,

as per the doc http://www.symantec.com/business/support/index?page=content&id=TECH178490 , I upgrade linux clients to 7.5.0.3 from NBU master.

currently our NBU master and media server are running NBU7.5.0.3;

Master:  [root@lx0034nbumast iyang]# cat /usr/openv/netbackup/bin/version
              NetBackup-RedHat2.6.18 7.5.0.3
Media : [root@lx0034nbumed01 ~]# cat /usr/openv/netbackup/bin/version
            NetBackup-RedHat2.6.18 7.5.0.3

and clients are running with NBU7.1 or 6.5.

[root@lx0034nbumast ~]# /usr/openv/netbackup/bin/admincmd/bpplclients -allunique -noheader |grep Linux |grep fin > clients_name

[root@lx0034nbumast iyang]# cat clients_name   ====>I only pick 2 boxes
Linux RedHat2.6 client1
Linux RedHat2.6 client2

[root@lx0034nbumast iyang]# /usr/openv/netbackup/bin/update_clients  -ClientList clients_name     
There are 12 clients to upgrade.
Do you want the bp.conf file on the clients updated to list this server as the master server? [y,n] (y)
Enter the number of simultaneous updates you wish to take place [1 - 2] (default: 2): 
The upgrade will likely take 1 to 2 minutes.
Do you want to upgrade clients now? [y,n] (y)
Please be patient.
Updating client client1-- Linux hardware running RedHat2.6
Updating client client2-- Linux hardware running RedHat2.6
The update trace can be found in /tmp/update_clients.09-06-2220.14843.

[root@lx0034nbumast iyang]# cat  /tmp/update_clients.09-06-2220.14843    
Will not update client client1
        client1 is defined as a client type from an earlier release of NetBackup.
Will not update client client2
       client2 is defined as a client type from an earlier release of NetBackup.

Any one who can help point theright direction?