If your Drupal 6 administration page returned blank page or the page is very slow, your site's server might have a problem to access drupal.org to check for available update for your Drupal 6 installation. Usually, the Drupal's Update Status module will check for theme and modules updates once in a day, depending on how you configure cronjob for Drupal. If updates cannot be performed, Drupal will check for updates every time you access Drupal's administration page.

This post will show you on how to disable Drupal 6 Update Status module using phpMyAdmin (I assume you use MySQL for your Drupal installation) even if you cannot access the module administration section of Drupal. This will enables you to access the administration page until the problem of your site's server cannot access drupal.org is solved.