[rhelv6-list] Dell servers stopping at GRUB if no manual input

[Ben]

I have a few Dell servers of varying marques: R710, R420, etc.  I've 
installed RHEL6 (64bit) on them via DRAC/serial console.  The grub.conf 
looks like this:

default=0
timeout=5
serial --unit=1 --speed=115200
terminal --timeout=5 serial console
title Red Hat Enterprise Linux Server (2.6.32-358.11.1.el6.x86_64)
         root (hd0,0)
         kernel /vmlinuz-2.6.32-358.11.1.el6.x86_64 ro root=/dev/mapper/vg_pinky-lv_root rd_NO_LUKS  KEYBOARDTYPE=pc KEYTABLE=uk LANG=en_US.UTF-8 rd_LVM_LV=vg_pinky/lv_swap rd_NO_MD SYSFONT=latarcyrheb-sun16 crashkernel=auto console=ttyS1,115200 rd_LVM_LV=vg_pinky/lv_root rd_NO_DM
         initrd /initramfs-2.6.32-358.11.1.el6.x86_64.img
title Red Hat Enterprise Linux (2.6.32-358.el6.x86_64)
         root (hd0,0)
         kernel /vmlinuz-2.6.32-358.el6.x86_64 ro root=/dev/mapper/vg_pinky-lv_root rd_NO_LUKS  KEYBOARDTYPE=pc KEYTABLE=uk LANG=en_US.UTF-8 rd_LVM_LV=vg_pinky/lv_swap rd_NO_MD SYSFONT=latarcyrheb-sun16 crashkernel=auto console=ttyS1,115200 rd_LVM_LV=vg_pinky/lv_root rd_NO_DM
         initrd /initramfs-2.6.32-358.el6.x86_64.img

Whenever I reboot them and I'm not connected to the serial console (or have 
a keyboard and monitor plugged in) and don't press <space> and/or <return> 
at the point at which it says "Press any key to continue." to get the GRUB 
boot menu up, the servers don't boot.  They just appear to stop at some 
point and are non-responsive via any method (connecting to the DRAC/serial 
console, or plugging in a keyboard and mouse) until rebooted.

Any ideas why, please?  This didn't used to happen with RHEL5, I don't 
think.

Ben
-- 
Unix Support, MISD, University of Cambridge, England