Hi,
I am using dual monitors, and this behavior has occured on 2 different computers (using the same monitors).
When I turn the monitors off, and then on again after a while, 1 monitor turns on, displays the Dell logo etc. but doesn't display the windows login. It is just a blank page, and then the green light turns orange.
Turning it on/off many times or just waiting a while eventually results in it working again, but I am very confused why!