Adam,

We found the issue.

If we use the insert media button, we can browse the folders by single clicking.

When we click the insert flash button, we can browse. But we have to double click the folder we want to open. After that we can browse by single clicking the folders.
If we click the insert flash button and select a flash file for preview, then we can browse by single clicking the folders.

In short:
We can browse the folders by single-click when 'insert flash' is clicked.
But we first have to

- select a flashfile for preview
or
- double click the first folder we want to open

I have also tested this at http://cutesoft.net/example/general.aspx