the problem i have with it is that when i put in a fully charged battery their is no life in the camera, it was working fine a few days ago , any ideas what the problem could be.
Had a check around the sites for you and the commont faults that would make the 20D not power up would be
Battery Pack maybe a little loose.
If the CF door is slightly “Off” that could do it.
If the camera had reset itself, that could cause an ERR99 message.
Ca happen if a faulty CF card is used (try another one) Make sure its off when switching.
Contact pins in the CF compartment are bent and sends a message to camera.
I took out the battery, removed the lens, removed the memory cards, left it for 10 min and then put everything back together. It then worked fine, and I have had no further issues.
Try cleaning the contact points between the lens and the Camera that might be one possibility,there are 3 contact points when you take off the lens and look directly at the camera front.Re-connect lens and start up again.