The same is happening to me on the netbsd3 branch.

Feico.

# create  bootfloppy/boot1.fs (from: boot  netbsd)
PAX=/mnt/usr/src/obj/tooldir.NetBSD-3.1_STABLE-i386/bin/nbpax sh
/mnt/usr/src/distrib/common/buildfloppies.sh  -i
"/mnt/usr/src/obj/tooldir.NetBSD-3.1_STABLE-i386/bin/nbinstallboot
-mi386 @IMAGE@ /mnt/usr/src/obj/destdir.i386/usr/mdec/bootxx_ustarfs"
-p  -m 2 -s .fs  boot 2880 boot  netbsd
Running instboot:
/mnt/usr/src/obj/tooldir.NetBSD-3.1_STABLE-i386/bin/nbinstallboot
-mi386 floppy.28655.tar
/mnt/usr/src/obj/destdir.i386/usr/mdec/bootxx_ustarfs
Free space in last tar block: boot 420, netbsd 305,
buildfloppies.sh: Image is 228145 bytes (222 KB) too big to fit on 2
disks

*** Failed target:  boot1.fs
*** Failed command:
PAX=/mnt/usr/src/obj/tooldir.NetBSD-3.1_STABLE-i386/bin/nbpax sh
/mnt/usr/src/distrib/common/buildfloppies.sh -i
"/mnt/usr/src/obj/tooldir.NetBSD-3.1_STABLE-i386/bin/nbinstallboot
-mi386 @IMAGE@ /mnt/usr/src/obj/destdir.i386/usr/mdec/bootxx_ustarfs"
-p -m 2 -s .fs boot 2880 boot netbsd
*** Error code 1

On Fri, Mar 02, 2007 at 12:28:34AM +0100, Andreas Burghardt wrote:
> Hello,
> 
> I made a build of netbsd-4 with an up-to-date cvs:
> 
> Running instboot: /usr/obj/tools/bin/nbinstallboot -mi386 floppy.6477.tar /usr/obj/dest/usr/mdec/bootxx_ustarfs
> Free space in last tar block: boot 44, netbsd 503,
> Writing 4423680 bytes (4320 KB) on 3 disks, padded by 1444864 bytes (1411 KB)
> Creating disk 1 to boot1.fs
> Creating disk 2 to boot2.fs
> Creating disk 3 to boot3.fs
> 0+1 records in
> 1+0 records out
> 1474560 bytes transferred in 0.007 secs (210651428 bytes/sec)
> Final result:
> -rw-r--r--  1 root  wheel  1474560 Mar  2 00:14 boot1.fs
> -rw-r--r--  1 root  wheel  1474560 Mar  2 00:14 boot2.fs
> -rw-r--r--  1 root  wheel  1474560 Mar  2 00:14 boot3.fs
> all ===> etc/i386/floppies/bootfloppy-big
>      create  bootfloppy-big/USTAR.volsize.13200
>      create  bootfloppy-big/boot (from: /usr/obj/dest/usr/mdec/boot)
>      create  bootfloppy-big/netbsd (from: /usr/obj/obj/distrib/i386/instkernel/netbsd-INSTALL.gz)
>      create  bootfloppy-big/boot-big1.fs (from: boot USTAR.volsize.13200 netbsd)
>      Running instboot: /usr/obj/tools/bin/nbinstallboot -mi386 floppy.3091.tar /usr/obj/dest/usr/mdec/bootxx_ustarfs
>      Free space in last tar block: boot 44, netbsd 503,
>      buildfloppies.sh: Image is 14327 bytes (13 KB) too big to fit on 1 disk
> *** [boot-big1.fs] Error code 1
> 1 error
> 
> nbmake: stopped in /usr/src/distrib/i386/floppies/bootfloppy-big
> *** [all-bootfloppy-big] Error code 2
> 1 error
> 
> nbmake: stopped in /usr/src/distrib/i386/floppies
> *** [all-floppies] Error code 2
> 1 error
> 
> nbmake: stopped in /usr/src/distrib/i386
> *** [all-i386] Error code 2
> 1 error
> 
> nbmake: stopped in /usr/src/distrib
> *** [snap_post] Error code 2
> 1 error
> 
> nbmake: stopped in /usr/src/etc
> *** [release] Error code 2
> 1 error
> 
> nbmake: stopped in /usr/src
> 
> ERROR: Failed to make release
> *** BUILD ABORTED ***
> 
> 
> Regards,
> 
>    Andreas Burghardt