I have received a few inquiries from website members and even experienced this in a workshop recently -- having dealt with this in the Casablanca Lab, here is the problem and the solution:

When attempting to export video onto a USB drive (Flash drive or thumb drive) I have had the system display a menu with something like 'Container Error'... which basically means (as I understand it), the device has not been successfully booted or mounted. 

To cure this, I recommend the following:
 

1. With your USB device inserted in the USB port of your Casablanca editor
2. go back to the Media Manager main menu (click the tiny interior right trackball button to get there quickly).
3. Click on the green USB icon at top center ('USB-Access external USB-Devices)
4. It should then seek and display the device by name (example: 'Kingston')
5. Click OK to open the device - this should mount or connect the device.
6. You can now go back out to the Media Manager main menu (click the tiny interior right trackball button to get there quickly).
7. Then re-enter the Video Archives to successfully export your video file/s onto this USB device