AMD64_GENERIC make buildkernel issue

[Neil Booth <neil@xxxxxxxxxxxxxxx>]

I've just completed a buildworld and am trying to build a kernel;
I get the following.  What am I doing wrong?

Neil.

neil@athlon2:/usr/src$ sudo make buildkernel KERNCONF=AMD64_GENERIC

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>>> Kernel build for AMD64_GENERIC started on Sun Aug 23 20:10:57 JST 2009
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===> AMD64_GENERIC
rm -rf /usr/obj/usr/src/sys/AMD64_GENERIC
mkdir -p /usr/obj/usr/src/sys
cd /usr/src/sys/config;  PATH=/usr/obj/usr/src/ctools_i386_i386/usr/sbin:/usr/obj/usr/src/ctools_i386_i386/usr/bin:/usr/obj/usr/src/ctools_i386_i386/bin:/usr/obj/usr/src/ctools_i386_i386/usr/games:/usr/obj/usr/src/btools_i386/usr/sbin:/usr/obj/usr/src/btools_i386/usr/bin:/usr/obj/usr/src/btools_i386/bin:/usr/obj/usr/src/btools_i386/usr/games  config  -d /usr/obj/usr/src/sys/AMD64_GENERIC  /usr/src/sys/config/AMD64_GENERIC
Warning: device "npx" is unknown
*** Error code 1

Stop in /usr/src.
*** Error code 1

Stop in /usr/src.