Hi HomerJ,

Are you set as a project admin or a system admin within site admin (your user being a domain admin has nothing to do with anything within HP ALM as well)?

If you are a project admin solely then you will not have access to the siteadmin section.

In order to be able to log in with the site admin user, you would have to have that account added to the LDAP system and then be bound by the rules of the LDAP system (and I wouldn't recommend doing that as it could cause issues in the future when trying to upgrade and such, it is best to keep it as a QUALITYCENTER authenticated user only).
What you will need to do correct issues is to change the authentication back to QUALITYCENTER on the DB instance and then restart the services. Once this is completed you can then log into the system as the original admin user and then go into the Site Users tab and select the red users Icon (it is the site admin users account group) and add your user to that group), once that is done then you can re-enable the LDAP through the settings and you should be able to log into the site admin with your user. A hint is to not log out of Site Admin once you have changed the authentication back to LDAP, as you can open another browser or tab to test the LDAP authentication is working correctly and if something is wrong and doesn't work you can still continue to make changes on the original login so long as you remain logged in (if you log out then you will need to change the authentication back again and start fresh).

Hope this helps,
Dan