When booting from a 64bit Linux live CD and chrooting into my Debian AMD64 I get a segfault in Grub. I run the grub shell and enter:
root (hd0,4)
setup (hd0)
To prevent the setup command from segfaulting Grub, the live Linux needs to be booted with the following kernel parameter:
noexec=off
This seems to be a bug in Grub.