Migration from 5.x-1.x to 6.x-2.x is broken

Because Drupal 6 uses menu names that were based off the menus’ titles and Menu block 5.x-1.x wasn’t storing the menus’s titles (it only stored the menu id, or mid), the specified menu from Menu block 5.x-1.x was lost in the conversion.

The just released Menu block 5.x-2.x fixes this by storing the menu title for the sole purpose of making the D6 upgrade possible without data loss.

In order to upgrade a site using Menu block 5.x-1.x to a Drupal 6 site, users must upgrade to Menu block 5.x-2.x before upgrading to Drupal 6.