I went to a bereavement session last month and I tried to use my 50mm 1.8 on my canon 40d but it wouldnt focus or move at all. I was so glad that I remembered to put in my other lens on my way out at 12am. Is there anything that I can do or check to see if this lens is no good anymore? I really love this lens and I if its no good Im will need to buy another one ASAP.