I figured even before reading http://plugable.com/2014/03/06/displaylink-usb-2-0-graphics-adapters-on-linux-2014-edition that DisplayLink won't work with proprietary nVidia driver. I also see that the USB monitor (and AOC) is activated while the machine is booting. As soon as the proprietary driver kicks in, it blanks out.
If I enable nouveau driver and reboot the machine, only the USB monitor shows the graphical display, and my notebook's monitor remains blank. When I look into Unity's standard "Displays" settings, only the AOC monitor is detected. (When I run proprietary nVidia driver, only the Built-in Display is detected). The color depth is very low though, but I wouldn't mind that too much as a secondary monitor. I know it's not for gaming or video.
Could anyone help with this? I'm running latest stock kernel of 64bit ubuntu: uname -a: Linux erebus 3.13.0-46-generic #79-Ubuntu SMP Tue Mar 10 20:06:50 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux
I can provide any other logs if needed, but I don't want to unnecessary clutter this post in advance. I hope someone else already got it working with this combination: Ubuntu 14.04 64 bit, nVidia GPU and DisplayLink monitor.