Canon 40D - Reduced Menu and Fixed ISO

Hi, I am really hoping someone can help. I am at my wits end having wasted much of my Sunday searching the internet.

I have a Canon 40D DSLR which I have had from new, is in good general condition, but it has not been used for a while. As I try to relearn the camera I have noticed two issues
1. I can not change the ISO setting, seems stuck at 400
2. I am unable to access the camera's menu when in any manual mode; the O, Tv, Av, M etc. When in basic and auto mode pressing the menu button brings up the menu, select any of the above manual modes and the many button does nothing.

I have taken both batteries out and let the CMOS die, I have tried to access the Setup 3 menu to "Reset" the camera but it is not presented in the options of the menu I can access. Even holding down the Menu and the Jump buttons does nothing. In addition, when in manual mode, none of the front buttons, the WB, AF/Drive, ISO/Flash buttons seem to work. The light button is ok and the wheels both front and back adjust the aperture and Shutter speed settings. But I can neither lower the ISO below 400 nor access the more advanced menus to perform a "Reset Camera Settings". I am not convinced this is an "Ex-Camera", that has is "Ceesed to be" I am sure I am just being stupid.

Any help and guidance would be greatly appreciated.

C00LH4ND