[dasymington]

I've been able to reproduce this with the following steps:

1. Hoist an item which has My Data as its immediate parent.

2. Add a text child item and hoist it.

3. Delete the new item.

It appears you can't do anything else now; you can't move to any other item and the Data Explorer pane is blank. If Ultra Recall has not stopped responding (which it did the first time) you can close the database and then open it again.