If you're getting a blank page when you are trying to access SharePoint Central Administration site, then check your IIS settings. To be more specific, check the authentication settings for SharePoint Central Administration website in IIS. Make sure that you have Windows Authentication enabled and Anonymous Authentication disabled.
This must be the shortest blog post I have ever written. But taking into consideration that it was written on the first day of work after the holiday season, it's not so bad. Happy New Year everyone!!! J