For the past 2 weeks-ish, my 40D has been malfunctioning and rarely working. On occasions, with fresh and fully charged batteries, it'll take a few pictures (the most I've gotten was ~25) and then it automatically turns off and furthermore the shutter stays open. I have to take the battery out, put it back in, and then turn it on for the the shutter to reclose. Also since I use Av, whenever I try to take a picture that's not wide open (i.e. f/2.0 on my nifty) it automatically does the shutter thing. I've changed the small backup battery and I feel as if it is something with my CF card, but this is really bugging me. I plan on taking it to a shop sometime soon, but I really don't want to. Does anyone know what's happening?
edit: Sometimes I am able to take a few pictures, turn it off and then it'll save the pictures, but if I don't remember to turn it off and it just shuts off on its own, all my previous settings and the pictures I took during that session are gone.