Does your flat panel display the POST? If not, you have to solve the problem of your monitor getting no display signal at all. If you do see the BIOS post and the display disappears once Ubuntu starts booting, odds are your are in a VGA framebuffer mode that the monitor doesn't support. See https://wiki.ubuntu.com/FrameBuffer for dealing with framebuffer issues. If you see Linux booting and your display disappears when X11 (GUI login) starts, you will have to reconfigure your X server into a display mode the monitor supports. Try switching to a text console (Ctrl+Alt+F1). If this doesn't work, reboot into single user mode (recovery mode on your GRUB screen.) If you have previously installed ssh-server on your Ubuntu computer you can ssh in from another computer as well.