@andresmcid, that probably means that your video card couldn't be configured automatically. There might be some way to troubleshoots these problems in the ubuntu forums, but usually you should be able to run X by just editing /etc/X11/xorg.conf and changing the Driver line to load vesa instead of whatever it's configured right now.
How to launch the installer after that... I don't know. I don't use ubuntu, so can't help with that.
@themanwhowas, that might work in other OSes, in linux we fix the things instead of reinstalling (well, the people at ubuntu forums are the exception sometimes
). Plus, if X doesn't work with the default config, reinstalling is not going to help at all.