Lync 2013 Polycom CX600 unable to sign in

Hi there,

I get an error on my Lync Polycom CX600 when signing in with a specific user with different SIP domain. The error on the phone is as follows.

Sign-in Error

Cannot Sign-in. Please verify your sign-in address. domain\user name, and password, and try again. PLease verify that the domain entered is correct.

When siging in with a user with a different user with different sip domain everything works fine.

Test-CsPhoneBootstrap works fine.

Test-CsClientAuthentication works fine as well.

I also checked the remote log from the phone and the only error i see there is "Error: hr = 80070490 - Failed to delete cred" but i cannot explain.

Any one any idea?