A the grub menu, select the entry you want to edit and press e
You'll get a menu with all boot commands for that entry, select the kernel line and press e
again which gets you a line editor. Move to the end of the line, remove the splash and quiet options and either append single
then press Escape followed by b
Now it should boot into single user mode.
While I'm here, does anyone know how to choose and permamently select a kernel version for bootup?
The best is to edit /boot/grub/menu.lst and move your desired entry to be the fist entry and set/leave the default
option at 0. Otherwise you can set default
to the number of the entry you want to boot by default (but that way has some drawbacks)