Passwords are designed to expire - so it is worth checking what the expiry value is as it may be that someone has configured a short expiry time and the system is behaving as it should.
This value is found in the Policy -> Rule Elements -> Authenticators screen (select the Password element).
I'm not aware of a problem where passwords expire randomly. But as you are running 7.0.1.02 I would recommend installing the current patch - 7.0.1.03
If having done this, the symptoms persist then I'd recommend you raise a service request with McAfee support.