I tried to restore my previous config to the 9746 module and libs with the 'right' xorg which causes the problem. An so It happened ! Attached is the log file you requested.
There are two problems :
1.- Memory leaks. When removing both 9746 and 9631 the kernel informs
that the module didn't freed some allocation it made.
2.- Xorg and beryl eating all the cpu they can get. With 1.2.99 version
of xorg-server (xorg-server-snap in the port tree) the one that goes mad is
the Xorg proces, which must be killed by root. With the stable version of
the xorg server is beryl the one which is hungry. In this case Xorg logged
this to the Xorg.log file :
(EE) NVIDIA(0): Failed to attach to shared memory segment 655467.
Sometimes I had seen this messages many times. It happens as soon as I start using beryl (one minute or two are needed to cause the problem).
have very big figures for both shmall and shmmax (taking into account that shmall is in pages and shmmax in bytes), to prevent this problem :
I'm reverting my config to 9631. Then I'll try to change some configs I have in min and inform of my results.