The standard Google Apps URL for your domain’s Control Panel (https://www.google.com/a/DOMAIN.NAME/) has a nasty redirect-loop, preventing successful login:

     Firefox has detected that the server is redirecting the request for this
     address in a way that will never complete.

Technically, you are receiving a HTTP status 310, redirect error:

     Error 310 (net::ERR_TOO_MANY_REDIRECTS): There were too many redirects.

Fortunately, there is another way to access your Control Panel: log on to Google Mail using an Administrator-account for your domain:

     <a href="https://mail.google.com/a/DOMAIN.NAME/" target="_blank">https://mail.google.com/a/DOMAIN.NAME/</a>

There, you should find a “Manage this domain” link in the upper right hand corner. It will take you to the Control Panel.

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