Comment 30 for bug 1546641

I have been facing this issue for a while now.

Some details of my system are as follows:

System: Host: sitspak Kernel: 4.4.0-22-generic x86_64 (64 bit) Desktop: Unity 7.4.0
           Distro: Ubuntu 16.04 xenial
Machine: System: Hewlett-Packard (portable) product: HP ZBook 15 G2 v: A3009DD10303
           Mobo: Hewlett-Packard model: 2253 v: KBC Version 03.10
           Bios: Hewlett-Packard v: M70 Ver. 01.07 date: 02/26/2015
CPU: Quad core Intel Core i7-4810MQ (-HT-MCP-) cache: 6144 KB
           clock speeds: max: 3800 MHz 1: 2805 MHz 2: 2801 MHz 3: 2800 MHz 4: 2987 MHz 5: 2800 MHz
           6: 2800 MHz 7: 2808 MHz 8: 2879 MHz
Graphics: Card-1: Intel 4th Gen Core Processor Integrated Graphics Controller
           Card-2: NVIDIA GK106GLM [Quadro K2100M]
           Display Server: X.Org 1.18.3 driver: nvidia Resolution: 1920x1080@60.01hz
           GLX Renderer: Quadro K2100M/PCIe/SSE2 GLX Version: 4.5.0 NVIDIA 361.42

I have observed following:

1. This happens when a external usb webcam is attached; dmesg regarding camera is as follows.

uvcvideo: Found UVC 1.00 device A4 TECH HD PC Camera (0ac8:3500)
[ +0.000882] input: A4 TECH HD PC Camera as /devices/pci0000:00/0000:00:14.0/usb3/3-10/3-10:1.0/inpu
[ +0.000116] usbcore: registered new interface driver uvcvideo
[ +0.000002] USB Video Class driver (1.1.1)

2. My themes fall back to classic gnome as well. To get around I restart lightdm service.
3. It was worse in Ubuntu 15.10 but in 16.04 some window decorations, icons & fonts fall back.
4. A dmesg related to Nvidia which might be interesting:

ACPI Warning: \_SB_.PCI0.PEGP.DGFX._DSM: Argument #4 type mismatch - Found [Buffer], ACPI requires [Package] (20150930/nsarguments-95)

Hope this helps!