I borrowed a 5D Mark III from a friend to use as my primary camera on a shoot, while using my 60D as secondary camera. At some point during the shoot, my SD card (32 GB) on the 60D went full, so I took the empty SD card from the 5D Mark III and put it in my 60D (I was shooting video on the 5D CF card, not the SD).
That's when everything went to HELL! I didn't know that my friend had installed ML on his SD Card… So when I inserted it into the 60D and turned the camera back on, the camera displays opened up for a second before going dark. Since then, my camera has been dead. I've tried removing the battery, removing the card, trying different SD cards, trying at least four different batteries (Canon and also 3rd-party), etc etc. NOTHING. The camera doesn't turn on, it doesn't shoot, and the displays stay dark all the time. The only thing that shows up, is a single red light flash each time I insert a battery and close the lid…
My guess is that the ML firmware that was installed for the 5D Mark III on the card might have corrupt my 60D?? But I really don't know much about ML, and I don't know how it works and how to reset my 60D. It is my primary camera all year-long, and I'm going to need it in less than a week for a 4-day shoot! =S