You can try to boot into safe mode. Hold down the shift key when you boot, and don't let it up until you see the white screen go away.
As memory serves, you will get to a screen prompt (kind of like a DOS prompt), with a blank and white screen. If you can get there, then logout (type exit or logout), and see if it reboots properly...
Sometimes just logging into safe mode will reset things.
It sounds like the software is hung up during the boot process, which is why you are stuck on the white screen.