I would say one of 2 things ... your motherboard is giving the wrong info because sensor is all wrong or sandra is not reading your board correctly. easy test would be, does it give "normal" temps using any other program?
That's the"wrongest" reading I've ever heard of. Check in the bios at start up to see what the MB thinks the sensor is saying. If that's way off the MB sensor is hosed. If the bios reads good Sandra is hosed.
One other possibility. If you're using a hacked bios it may be wrong. Also, make sure the bios is the latest version (somebody, I don't think it was ASUS) had to do a bios temp sensor patch this fall.