If you are ever in a situation where you want to find out if you logged into using cached domain credentials (AD) or authenticated against the domain controller then the easiest way is to open Event Viewer and look for the entry where the source is NETLOGON and Event ID 5719.
The description would be something like:
Log Name: System
Date: 27/05/2011 08:53:17
Event ID: 5719
Task Category: None
This computer was not able to set up a secure session with a domain controller in domain YOUR-DOMAIN-NAME due to the following:
There are currently no logon servers available to service the logon request.
This may lead to authentication problems. Make sure that this computer is connected to the network. If the problem persists, please contact your domain administrator.
If this computer is a domain controller for the specified domain, it sets up the secure session to the primary domain controller emulator in the specified domain. Otherwise, this computer sets up the secure session to any domain controller in the specified domain.
Here is a screenshot (on Win 7) showing a (filtered) view of the same event.