make -j12 all fails in uImage target

[Olaf Hering]

this is what I got with 2.6.11rc3:

make ARCH=ppc O=../O-2.6.11-rc3-b50-SMP -j12 all
...
  LD      vmlinux
  SYSMAP  System.map
  SYSMAP  .tmp_System.map
  OBJCOPY arch/ppc/boot/images/vmlinux.bin
  HOSTCC  arch/ppc/boot/utils/addnote
  HOSTCC  arch/ppc/boot/utils/mknote
  HOSTCC  arch/ppc/boot/utils/mkprep
  LD      arch/ppc/boot/lib/built-in.o
  HOSTCC  arch/ppc/boot/utils/hack-coff
  HOSTCC  arch/ppc/boot/utils/mkbugboot
  OBJCOPY arch/ppc/boot/images/vmlinux.bin
  GZIP    arch/ppc/boot/images/vmlinux.gz
/bin/sh: line 1: arch/ppc/boot/images/vmlinux.bin: No such file or directory
make[2]: *** [arch/ppc/boot/images/vmlinux.gz] Error 1
make[1]: *** [uImage] Error 2
make[1]: *** Waiting for unfinished jobs....

also, one time that zImage.chrp was only 570K instead of the expected
1.4M, so netboot failed. But I got no build error.
Any idea what dependency is missing?