Run
make buildworld and
make installworld
fusefs-kmod won't run properly if userland has not been updated too.
Code:
# cd /usr/src
# make buildworld
# make buildkernel KERNCONF=MYKERNEL
# make installkernel KERNCONF=MYKERNEL
# reboot
--- after reboot ---
# cd /usr/src
# mergemaster -p
# make installworld
# mergemaster -iU
# make delete-old
# make delete-old-libs
# reboot
More info - the FreeBSD Handbook
http://www.freebsd.org/doc/handbook/makeworld.html