Unrecoverable DB error when modifying Custom Data type

Replicated in the Joomla Demo install.

Create a new Custom Data set (in this example, called Extended data). Create as an Individual type. Add 1 field.

Change to Participants type. Save.
Change to Participants (Role) type. Save. Error displayed.
Try to change back to Participants type, no error on save, but if you view the Settings, the type has not changed (Participants Role still displayed).

Back trace logs from my personal encounter with the problem are at:
http://forum.civicrm.org/index.php/topic,18516.msg76943/topicseen.html#msg76943