SGN_6.1 cannot encrypt External Hardisk

Hi,

I Have a problem on our External Hardisk, we cannot encrypt the files Using USB encryption policy.

The scearion is this,

                                after we installed SGN_client we enable USB encrpytion policy

                                I attached the external hardisk to the machine in order to encrypt the files.

                                 I notice is after one nimute it will closed the notification box that  is starting for and encrytion and after one  nimute again it will  open the notification box to  start the encryption again.

                                 It will start and closed the box for the encryption again and again.

It is their a way to  fix this problem?

Please advice.

Thank you:)

tedz