This morning, my mom logged into her computer as normal, used Mail to check her email, and then got distressed when seeing "squiggles and lines" on her monitor. When trying to restart her machine, it always fails. The apple logo and loading bar come up, it loads to completion, and then the gray screen (no Apple logo) just hangs for a minute or two. Then it turns off. I can't boot into Safe Mode, and I've tried a NVRAM reset (for 3 chimes). She has a backup as of about a month ago, but I'd rather not wipe everything if at all possible. What could have caused this?