Boot Options for LiveDVD

Hi:Can any one give me an URL with the boot options (cheat codes) for Ubuntu Live 5.1? I did a search with Google but found nothing.I need to load the vesa driver at boot. I have a system freeze after X starts and I believe this is due to my graphics card, an ATI Radeon X600 pci express.I tried already "xmodule=vesa", "vga=normal" but it didn´t work. I also tried to boot in text mode and change the xorg.conf. I did "init 3" and it didn't work also.Is it possible that the "live" option doesn't accept any cheat codes?Thanks.Joao