Then it locks up hard, so it seems that the 3-stable kernel doesn't
work with the current userland.
Running a -STABLE kernel with an -CURRENT userland is a bad idea. As a
matter of fact, running a kernel older than your userland is surely
asking for trouble. This doesn't hold the other way round (usually),
that's why you first upgrade your kernel and then your userland. FYI:
http://netbsd.org/Documentation/current/#what-to-do
defaults fix:
/mnt/newetc//usr.sbin/pf/etc/defaults is not a directory;
skipping check
Migrate /usr/X11R6/lib/X11/twm to /etc/X11/twm [NOT FIXED]
Migrate /usr/X11R6/lib/X11/xdm to /etc/X11/xdm [NOT FIXED]
Migrate /usr/X11R6/lib/X11/xinit to /etc/X11/xinit [NOT FIXED]
Migrate /usr/X11R6/lib/X11/xserver to /etc/X11/xserver [NOT
FIXED]
Migrate /usr/X11R6/lib/X11/xsm to /etc/X11/xsm [NOT FIXED]
[...]
postinstall fixes failed: defaults gid uid x11
These fixes failed, so your system isn't quite up-to-date. Usually
re-running postinstall with the failed fixes does the trick. If not, you
should be able to do these fixes manually (i.e. making the missing
directory, adding the missing groups/users, moving the x11 files, etc.)