I was shooting at night and my flash was working perfectly, all of a sudden I tried taking another picture and it stopped working. I was using it on ETTL mode, the pictures looked underexposed with no signs of flash, then I tried using it in manual, what happened next was an overexposed picture because of the flash's light. Because I realized it was kinda working in Manual mode I set the ISO to 100 and a very fast shutter speed and it did the job, but this means that there is no way I can use my flash with the right exposure. I tried using my flash on my canon 60D and it works perfectly. Hope someone can give me an answer?