Hi DCS1,
I'm sorry to hear your camera is frozen on. Looking at your message you already tried some of the things we would recommend. I do not see a mention on if you tried loading a different battery, memory card, or attaching a different lens on the camera. Sometimes if one of those pieces is malfunctioning it can cause freezing and power issues.
If the issue continues normally we would recommend sending the camera in for repair. Unfortunately the EOS 5D Mark II is out of service life, so repair options are no longer available for it. In that case the only option available through Canon for that camera model would be the Canon Upgrade Program.
Through the Canon Upgrade Program we would be able to generate a 10% discount code you could use to purchase replacement equipment. If you want use the Canon Upgrade Program you will need to call our sales team at 1-800-385-2155 from 9 a.m. to 9 p.m. Eastern time Monday through Saturday. They will also be able to assist you if you have questions about buying products, when products will be back in stock, and what products the discount code can be used on.
