Today I was trying to export a CCK and import it to another Drupal Installation, but I was getting a freaking error "An illegal choice has been detected. Please contact the site administrator".
Guess what, I'm the administrator :P
After debugging the import process I realized the fail is because by default all content types in a Drupal Installation with module Page Title enabled, have the option "Show field" unchecked. if this option is unchecked the export process for CCK generates a code like this: