First, thanks to all who replied and jonh, your question about the console going to the serial port proved quite prescient. Keeping copies of my grub.conf file at various stages of the process reveals that at the point of death grub.conf started: serial --unit=0 --speed=9600 terminal --timeout=10 serial console # grub.conf generated by anaconda # # Note that you do not have to rerun grub after making changes to this file # NOTICE: You have a /boot partition. This means that # all kernel and initrd paths are relative to /boot/, eg. # root (hd0,0) # kernel /vmlinuz-version ro root=/dev/hda2 console=tty0 console=ttyS0,9600 # initrd /initrd-version.img #boot=/dev/hda default=1 timeout=5 splashimage=(hd0,0)/grub/splash.xpm.gz hiddenmenu title Scientific Linux SL (2.6.9-34.ELsmp) root (hd0,0) kernel /vmlinuz-2.6.9-34.ELsmp ro root=LABEL=/1 acpi=off rhgb quiet console=tty0 console=ttyS0,9600 initrd /initrd-2.6.9-34.ELsmp.img Investigating further, I found that I had put SL_enable_serialconsole into my standard list of RPMS. Thanks again for all the help and do I assume that SL_enable_serialconsole is normally a safe thing to have installed? Presumably it's just a quirk of this machine or is this common? John