Well, Poser allows you to reduce the number of threads used, so it grabs all I allow it to.

It turned out that the latest drivers are just too aggressive, with some renders actually tripping the GPU itself and turning the screen black for a second. I just rolled back the drivers to the previous ones and it is all stable again. I'll be able to put Poser back on 12 threads without worrying about the rest of the system being unstable.

I do have a laptop, but the capacity difference between the desktop (i7 hex core, 64Gb RAM, 9 Tb disk space) and laptop (i5, 4Gb RAM, 500Gb disk) makes network render more trouble than it's worth.

Thanks for pointing out where the tile size is!