That would require changing data via database. Please try to access to your site database via PHPMYADMIN, and run this kind of SQL command:

[code]
UPDATE jos_eb_events SET event_type = 0, parent_id = 0 WHERE id IN (1,3,5,7)
[/code]

- Replace jos_eb_events with actual table name (change jos_ to the table prefix uses on your site)
- Replace 1,3,5,7 with ID of the events you want to update

Regards,

Tuan