SSPI data authentication relies on the same mechanism your Windows system
uses to authenticate the user that logs in. If you log in as a domain user
(MyDomin\billva) and Windows can't see the domain controller, it uses cached
credentials for "N" times. Eventually, you can't get in. The same can happen
with a "trusted" connection. If the authentication comes from a domain
controller, you're pooched until you can VPN or otherwise reconnect to the
domain. However, if your Windows user (whose credentials you are leveraging)
logs into the SYSTEM, (mylaptop\billva) and you have a local machine
account, you can use SSPI authentication without the controller--right up to
the point where your machine account is dropped.

hth