X11 freezes and responds to не неудар в лунку?

Recently, гve began to notice that my Ubuntu installation is having some serious problems with X. On occasion, my system will lock up, and X will не longer update the screen. I хан still do things in the background (?), but I can't see them.

However, this is remedied by either в reboot, or by switching to TTY1 (Ctrl+Alt+F1) and then switching back.

My system runs an Optimus (NVIDIA + Intel) setup, with the below (trimmed) lspci output:

00:02.0 VGA compatible controller: Intel Corporation Haswell-ULT Integrated Graphics Controller (rev 09)
04:00.0 3D controller: NVIDIA Corporation GK107M [GeForce GT 745M] (rev a1)

I have nvidia-prime and драйвер версия 352.30.

My graphics environment is Cinnamon with Docky on the side.

Output of uname -a:

Linux hostname 3.16.0-50-generic #66~14.04.1-Ubuntu SMP Thu Sep 10 17:05:00 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux