OK. I've now replaced the offending grub menu entry with this
title Gentoo Linux (rescue) root (hd0,4) kernel /boot/bzImage-2.6.28-tuxonice-r10 root=/dev/sda5 real_root=/dev/sda5 vga=0x315 video=vesafb:mtrr:3 console=tty1 softlevel=nonetwork
and added this line
password --md5 somethinggeneratedbymd5cryptingrubshell
to the header of the grub config file. Things are much better now.