Steps to reproduce:

1. Create a new space.
2. Go to Tools > Attachments and attach any .swf file.
3. Create a page, go to Insert > Other Macros > Multimedia Macro
4. You'll get No appropriate attachments
5. Save the page.
6. And if you go back to your Attachments you'll see that the .swf is gone.

Workaround.

If you add the same .swf for the second time, will work.