I have been having an issue with my canon EOD 40D. When less expected, during photo sessions the camera gets idle. No apparent reason. In order to put it back to work I have to detach the grip and remove the batteries. If I either remove the grip not removing batteries or I remove the batteries not removing the grip, the camera does not start working again. No error message .. simply gets idle. Please advice and or reason for this problem is greatly appreciated. Thank you in advance for your time.