I just took my old 550d out of the drawer wanting to sell it. Unfortunately I do not have a boot card any longer. Without a card the camera seems to work completely fine, I can access the menu, make use of all the functions and take pictures. But with an SD card (blank) inserted the screen goes and stays off and I can only use AF without taking pictures. I suspected that the problem is not having a bootable card so I tried to prepare one. Still nothing. Can you please help?