Note that the 7D will slow down considerably in bad lighting situations! This is independent of your shutter speed and aperture settings! To check, use with lens cap on: fps goes down to approx. 3/s. Point at a lamp or use in daylight: fps goes back to 7/s.

Follow these steps to fix the problem: Symptom: EOS 7D won't turn on. Battery is charged. Tried several batteries. Battery door closed. CF card compartment door closed. Diagnosis step one: Is the Lithium battery fresh? Replace and check. (My best bet here!) Step two: Clean the battery contacts in the battery compartment. In particular the silver one that is closer to the back of the camera. Use a screwdriver and slightly scratch any oxidations off the surface of the lowest, protruding part of the silver contact. After that clean with cotton swab and alcohol. Carefully clean the two copper contacts with cotton swabs and alcohol. Step three: If it still won't work or the camera fails again shortly afterwards, remove bottom plate and see if one or several screws of the bottom circuit board (towards the handgrip or towards the CF card door) fell out. Happened to my 7D, too. Shaking the camera and tapping with a screwdriver can remove the screw from the innards... Mind the flash capacitor! If none of this...

Chuck, what exactly do you mean be "eye piece is loose"? The standard Canon Eyecup Eg can become loose when one (or both) of the little plastic hooks break. You can get a new one everywhere for cheap (7$?). Make sure you press the sides of the eyecup when taking it off in order to prevent breaking the little plastic hooks. What exactly do you mean by "the LED screen protector falls off"? Best P

Follow these steps to fix the problem: Symptom: EOS 7D won't turn on. Battery is charged. Tried several batteries. Battery door closed. CF card compartment door closed. Lithium battery fresh. Diagnosis step one: Look at the top LCD. Is the battery symbol flashing? If yes, make sure your battery (including the Lithium battery) is charged, original, and new. If not (nothing at all showing on top LCD) proceed to step two. Step two: Is the viewfinder unusually dark? Manual focussing seems off? If yes proceed to step three. If no: The camera receives power but will not turn on because either the main switch, the microswitch of the battery door, the microswitch of the CF card compartment, or several switches are not working. Check those switches. Use screwdrivers to check the operation of the microswitches. Clean the main switch with a strong air blower while switching back and forth (sand!). Step three: If the viewfinder is unusually dark, the camera gets no power whatsoever (the 7D uses polarizers for the...