Canon 40D, battery and auto-focus

Hi,

I've got a Canon 40D and have not had any issues with it until yesterday. I was at a friends wife's 60th birthday party and was taking a lot of pictures for them.

I also charged the batteries the night before and made sure everything was ready for the party. I pretty much left the camera on all the time so I could just pick it up and shoot. I had taken 159 shots and got up just past the cake cutting. When it came time to open the gifts, my camera would no longer auto-focus or take a picture. I tried different lenses and still no go.

When I got home later that night, I started trying different things out. I should also mention that I could take pictures using manual focus, but not auto focus. I searched the web for any problems with the 40D. Found some stuff from 2007 about auto-focusing issues and it said to try removing the battery and put it back in. I did remove the battery, put in a second fully charged battery. Sure enough, the auto-focus started working again. The battery meter on the top of the camera indicated the original battery was still half full.

Anyone else had problems like this and was it really a low battery causing the problems? Is there a different problem with 40D's that would cause this?

Thanks...
Al

All I can think of is for you to clean the contacts on both lens & camera, and try again. What lenses were you using (you failed to specify, and I'm not going to try to guess).

Thanks for the reply Bannor.

I did clean both the contacts on the lens and camera. It was happening with both the 18-55mm IS kit lens and the 70-200mm F4 L lens. The camera would not auto-focus or snap a picture until I turned off the auto-focus on the lens. Then I could only take a picture while focusing manually. All other settings and controls appeared to work perfectly.

Al