5D MKII Problems, need help

Ok so I just bought a 5D MKII yesterday and today I was about to use it and at startup I am getting an error 80, nothing else powers on. So I took the battery out and now its fine. A few shots in and I get the error again and it fails to release the shutter and all of the buttons dont work. Repeat the process, sometimes it works and sometimes it doesn't. Sometimes the camera wont startup at all and by that i mean no error, just nothing turns on. Another thing im experiencing is sometimes when i do turn the camera on, the top lcd turns on but when i push a button it will flash "busy" forever"

What can I do and is their a fix for it? The camera has a very low shutter count and its almost brand new. Bought it used. My memory cards seem to write fine, I use 8GB Sandisk Ultra cards and my batteries are all authentic LP-E6. Someone help me. Thanks

error is attributable variously to memory cards and batteries.

https://photography-on-the.net …/showthread.php​?t=1171278

see the bottom of this page also:

http://www.canon-europe.com …13-917361&page=1&type=faq

and this one

http://www.fredmiranda​.com/forum/topic/11572​53

But if that is a primary reason, why would my camera not startup at all. Batteries are fully charged btw. And I havent had any corrupted pictures or any problem with photos writing to the card. Im stumped. Just dropped $1500 on this camera and this is very annoying

I had similar problems with a 5D I bought used. My solution? I used a pencil eraser to clean all the electrical contacts. Batteries, grips, body, all of it. Haven't had an issue since.