Same thing started happening to the 40D I bought used about a year ago, I tried different settings...sunny, cloudy, shade etc...I adjust the depth of field, shutter speed etc. but those don`t work. I shoot stationary subjects most of the time but it is beginning to get annoying, I`ve even been thinking of changing to the 6D, I want a FF camera so I`m reading up as much as I can, no decisions yet. Isoproply alcohol eh....I have no idea how to say THAT in Japanese so I may just take the camera to a chain shop, show them the problem and hope they`ll have an idea about what I mean....`course they may try talking me into buying a new camera too....but honestly, peer pressure hasn`t really played a role in my life for decades so that won`t work on me. Still, I`d like to know what`s going on since I have another 40D that doesn`t do that...the first I bought new when they came out so I`ve had it since then. So if it comes down to spending money to get it fixed, I may just spend that cash on a new body....depending on cost of course.