This issue was reported under 5.3/5.4 as well.
link
I see this issue in one of two ways.
1) with the USB dongle and screen attached, i can resurrect the screen by locking it, or pressing ALT+CTRL+DEL. If the screen is already locked, I have to remove the dongle and plug it back in.
2) with the USB dongle unplugged and a 2nd external monitor plugged into the VGA port on my laptop, i have no options. The screen is completely non responsive and will not turn back on. I have to force power down my laptop to get any screen to come back.
Machine:
Dell Precision M4500.
Windows 7 x64
nVidia Quadro 1800M
3 external Dell 2007FP's (when i'm in my office) - 3x DVI
1 external Dell 2007FP + Laptop screen (when i'm at my house) - 1x VGA
This issue is frustrating and bothersome as this hardware was recommended by Dell for use in my laptop. Please advise, I can provide whatever information is required on demand.
Thanks,