view::destroy() - Fatal error

On the latest stable 6.x installation, this props up when trying to access blocks.

Fatal error: view::destroy() [function.view-destroy]: The script tried to execute a method or access a property of an incomplete object. Please ensure that the class definition "views_plugin_display_default" of the object you are trying to operate on was loaded _before_ unserialize() gets called or provide a __autoload() function to load the class definition in /home/sampada/projects/drupal6/stock/views/includes/view.inc on line 1460