Nouveau - Mar 2016 - display freezes when mouse pointer hits left edge

Hi!

I have a very strange problem with a recently purchased ViewSonic 4k 
display connected via display port to a Thinkpad 410 with nvidia gt218m 
(nvs 3100m).

Every time the mouse pointer touches the left edge of the screen, the 
display becomes a block of solid color and freezes. Suspend/resume of the 
laptop reanimates the display. I suspected a bug in the handling of the 
hardware cursor, so tried disabling that via HWcursor false in xorg.conf, 
to no avail. HWcursor false leads to black screens (internal and external).

There are no related messages in dmesg or in xserver-log.

versions: X server 1.17.2, linux kernel 4.5.0, nouveau 1.0.12, dual screens 
active (also happens with external monitor active only, though that 
configuration is very unstable), does not matter if the external monitor is 
configured as "left", "right" or "top" to the
internal; did not try
"bottom".

Any Idea how I could further investigate this problem?

As a workaround, i create a pointer barrier via xfixes, that works for now.

TIA
Robert