Something I never experienced on my local setup suddenly happened on the production site: random white pages. Consistent in that it was always the same pages (e.g. admin/build/modules), but random because most content pages would show up fine and many admin pages as well.
Digging aroung showed an error in the Apache log:
Fatal error: Allowed memory size of X bytes exhausted
I found the answer here: http://drupal.org/node/76156. I added an appropriate ini_set line to settings.php and suddenly my admin/build/modules page showed up.