I purchased a 40d on Nov. 21, 2007 and quickly noticed a peculiar power problem. When using the camera in normal shooting conditions, it will show full battery life and then all of a sudden, it will shut down because of low battery. I would then turn the camera off and then back on and it would miraculously show a FULL battery life. What gives?
This threw me for a loop, so, i fully charged all three of my batteries and tried using it again. Within 50-100 shots, it did it again. I turned it off then on again and it showed full power. This happened repeatedly with all three different batteries. FYI, for most of my shots i was using my EF 85mm f/1.2L. The reason i mention that is because i am half suspecting a correlation between the lens and the battery problem.