In actual dedicated 'New post' windows, the icon for Add flash video shows up as expected. However, in my Quickpost gadget on my dashboard, it appears as plain text in Firefox (which prolly captures alt='' value), and as a broken image in other browsers. The link seems to lead to:
Weird. Behavior has been the same in WP 3.0.1-2-3. I will upgrade to 3.0.4 in a couple of minutes, but I honestly expect nothing but the same behavior. Anyways, this requires a minor fix.