5dmk2 battery icon says full then says empty and shuts down

[bokeh]

Hi,
After formatting a 16 gig card with ML I got Error 20. I could hear issues with what sounded like a stuck shutter or mechanical sound. Camera sat untouched for over 1 week.
Today I dont know why but it stopped reporting error 20 although it did report it earlier during the day.

Now when I load a battery with camera switched on I see all the icons for a split second. Batteries that flash green in the charger, also show as full for that split second and I then get the flashing flat battery icon and camera behaves as you would expect with a flat battery.

Initially I get the red flash once I close the battery door. Then the camera behaves as if the battery is flat, although it obviously isnt. I have 6 canon batteries and 1 non canon battery all doing the same thing. I have formatted card on my mac. I have added ML on the cards. I cant format cards in camera as it only stays on for 1/10th of a second before shutting down.
I have switched lenses and all that usual stuff. I've happily used ML consistently and mostly trouble free for a couple of years. By mostly, I mean I have only needed to eject the battery and that fixed any problem.

Has anyone experienced this battery issue? I have cleaned all battery terminals etc with a cloth.

Thanks,
Bokeh