Upgrade from Yosemite to el capitan 10.11.1 results in white empty screen.
My imac ended up in an empty white screen when it auto boot during installation.
Saw that on my mbp and the problem was vbox kextt.
But no vbox on imac.
It would be nice to have a small program that would list currently know problems.
So you can fix the problems ahead of time.
Now I do not want to upgrade before I know what may have caused the problem because it took 30 hours to restore from time machine.