I created a bug report about this 6 month ago here:
For some reason I can’t reply to it anymore, but I finally found the source and solution to this bug so maybe someone else might find this helpful or it will help NVIDIA to investigate the bug.
The problem was that with the NVIDIA driver the laptop would lock up randomly. This happened multiple times a day. I then switched to using nouveau, but also had lock ups. The fine folks at #nouveau told me to delete the libvdpau_nouveau.so files and this instantly fixed my problem. I did not have have problems for months. I was using XFCE, since Gnome + nouveau was really laggy and had some rendering artifacts. Now after a few months I wanted to go back to Gnome and reinstalled the NVIDIA driver and just 2-3 hours later I started getting lockups again. Now I uninstalled libvdpau and lib32-libvdpau on Arch with pacman -Rdd to override the dependency check and the problem is fixed for the NVIDIA driver aswell. I’m happily using NVIDIA + Gnome now for 2 weeks and did not have a single lock-up.
I don’t know why this happens and my card shouldn’t be capable of using VDPAU anyway, according to wikipedia, but getting rid of the libvdpau_nvidia.so files also solved the problem when using the proprietary driver. I also do not have any sideeffects from removing this dependency.