Are you saying that the top half of the photo was black, or is it the LCD?
If its a photo, does it look the same when viewed on the camera LCD screen? Is the issue the same for other memory cards?
A shutter issue sometimes starts with a black bar. It will appear at high shutter speeds, so you can out a shutter going bad by taking shots at 1/8000 sec and see if the bars show up frequently.
Shutter issues can pop up randomly, I've heard of people having multiple failures.
Since you have been thru this before, you probably have tried different card readers and cables to eliminate any issues there.
If you can't fix the issue, send the camera to Canon and let them tell you what needs to be fixed. Then negotiate on the repair price. Be polite, and ask for help, don't demand. You will likely have to talk to a manager, but they should give you some relief if its a issue they have fixed before.