not sure if you can help or not, but i bought a canon 7d in november and up until last week it was working great, no problems. it had always been awesome in low light, even when i took photos with barely any light, when i didn't think it'd have a chance, it always pulled it off.
last weekend, however, i tried to take a photo it should have had not problem with (bit dark, but had light from a window and from an overhead light) and the 50mm 1.4 hunted like mad. i tried standing in different spots, adjusting settings, tried taking photos of other things and it always had the same problem. i noticed this continued after a few days, no matter what lens i used, and today i was taking photos outside at noon an overcast day, and had to max out both aperture and shutter speed (iso roughly 200) to get any kind of decent photo.
i've tried two lenses, both had the same problem, so i know it's the body. full auto and aperture priority photos come out dark, too (and metering isn't on a bright spot).
any ideas why my 7d would suddenly have real trouble in low light? is there a setting i could have changed by accident to affect it? the body hasn't been damaged in anyway, and i tried googling but found nothing. i'm at a loss.