Canon Utility problem

Hi chaps, trying to use Canon utility for the first time to tether and remotely control my 5D MkII from my iMac (El Capitan), didn't work at first until I downloaded update for 'Utility' then all seemed fine but after a minute or two I hear the camera 'click' and it 'shuts down' ie all goes black, the connection is lost and I need to take the battery out of the camera to get it back to life .... anyone any ideas please ?

Thanks Roger

No real ideas, but two guesses...

Set auto power off to - NEVER
Reflash camera firmware ...

Thanks Bassat for taking the time, yes I had turned off auto power but I had old firmware which I have now updated, no difference I'm afraid.

Further trials are getting me to think it might be a non Canon battery I was using - it works for a couple of exposures and then shuts the camera down. Not totally convinced it's the problem but I'll keep experimenting. I'm also thinking about getting a mains adapter as the drain using live view in utility is dramatic.

I'll get back when I have time to confirm these thoughts.