I tried to use the Plex App on the FireTV (because its a lot nicer than the one on my Samsung Smart-TV), but unfortunately I wasn’t able to playback any video. I encountered the following message:

To fix that, go to settings and change the media profile to “enforce direct playback” (or something) and it will work. Seems my Plex server doesn’t want to serve to Android devices (my Plex server runs on a Synology box).

Have fun, it should work now.

This is shit. If you had plugged in an USB 2.0 device before plugging in the USB 3 disk, the port may stay in USB 2 mode.

How do I get the best performance from the USB 3 ports?
The first device you plug in will configure the port, so always connect USB 3 capable hubs or devices first.

http://support.apple.com/kb/HT5172?viewlocale=en_US#8

The only solution is to reboot the system. Happy, my disk is not broken, unhappy because this is shit.