AD user lockout

A Windows 7 users (user A) is using Outlook 2007 to access MS Exchange 2013 mailbox. In addition to the primary mailbox user has a secondary mailbox connected from another user (user B). user B is disabled in AD and user A has full mailbox access to user's B mailbox.

whenever user A attempts to access secondary mailbox he locks his AD account out.

Hotfix published here http://support2.microsoft.com/kb/2598366 has been applied to user's A computer.

is there a way to tell what option was requested by the client which received KRB5KDC_ERR_BADOPTION response from the domain controller?

Thanks you