If you try to install Scientific Linux 5.10 x86_64 with "bootloader
mbr", you will find it crashes during the "installing bootloader"
phase. This is because /sbin/grub from the grub package is dynamically
linked against non-existent libraries.

Doing "chroot /mnt/sysimage" and then "/sbin/grub" by hand results in:

  bash: /sbin/grub: /usr/lib/libc.so.1: bad ELF interpreter: No such
file or directory

If you manually run "rpm2cpio grub-0.97-13.11.el5_10.1.x86_64.rpm |
cpio -id", then "file sbin/grub", it says:

  sbin/grub: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV),
dynamically linked (uses shared libs), for GNU/Linux 2.6.9, stripped

This is clearly wrong; grub is supposed to be statically linked, not
dynamically linked. (If you do the same rpm2cpio + file sequence on
the grub package from SL 5.9 or earlier, you will see that it is
statically linked.)

This appears to be an instance of the following bug:

  https://bugzilla.redhat.com/show_bug.cgi?id=246827

Summary of the bug: If you build the grub SRPM on an x86_64 system
with the i386 ncurses-devel package installed, you wind up with a
dynamically-linked grub that requires the non-existent
/usr/lib/libc.so.1. It looks to me like SL 5.10 was built on such a
system, while earlier 5.x versions were not.

 - Pat