When I try to do a ctr-alt f(1-6) in ubuntu 12.10 I only get a black screen with a blinking cursor but no login prompt. Any ideas on what could be wrong? It is a fresh install of 12.10 using a amd radeon 5850 graphics card. i have tried different things in my /etc/default/grub but at the moment I use the following:

# If you change this file, run 'update-grub' afterwards to update
# /boot/grub/grub.cfg.
# For full documentation of the options in this file, see:
#   info -f grub -n 'Simple configuration'

GRUB_DEFAULT=0
#GRUB_HIDDEN_TIMEOUT=0
GRUB_HIDDEN_TIMEOUT_QUIET=true
GRUB_TIMEOUT=10
GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash vga=normal"
#GRUB_CMDLINE_LINUX="vga=0x0376"

#RUB_CMDLINE_LINUX_DEFAULT="vga=0x014c"
#GRUB_CMDLINE_LINUX="vga=0x014c"
#GRUB_GFXPAYLOAD_LINUX=1600x1200x24
# Uncomment to enable BadRAM filtering, modify to suit your needs
# This works with Linux (no patch required) and with any kernel that obtains
# the memory map information from GRUB (GNU Mach, kernel of FreeBSD ...)
#GRUB_BADRAM="0x01234567,0xfefefefe,0x89abcdef,0xefefefef"

# Uncomment to disable graphical terminal (grub-pc only)
#GRUB_TERMINAL=console