Not sure if it's the same as the MXQ boxes but I think it is. What you need to do is insert a toothpick or similar, nothing meta,l into the audio out socket and you should find there is a hidden button. So power off your box, insert SD card, insert toothpick into audio socket until it clicks down and then power on your box while holding toothpick in place. This should set your box up so that if the SD is in when powered on it will boot from the card.
I just tried it again, with the toothpick method i get the CWM menu. is it ok?