[van141]

I am not familiar with your box but atv1200 recovery screen has several choices and one of them allows you to browse for a file to start updating firmware. You could insert SD card once you boot to the recovery screen and select the relevant file. BTW this mode allows installation from usb key also, at least I believe so, you just have to know which file to select to run. SD card is normally stipulated for firmware installs because the 'box knows' to automatically look for firmware on SD, not USB port.

This is how the flashing to 'beta 1080p' firmware is done on Android 4.2, not sure if that might solve your problem. Check out the video where it shows the recovery screen options.
http://www.mygicasupport.com/viewtopic.php?f=84&t=1762