I had a bit of trouble burning CDs when I first started, but I found InfraRecorder
and that fixed it. The first couple of CD's that I burned have the contents of the ISO on them but are not bootable. The half-dozen CD-R's that I burned with InfraRecorder processed bootable Live-CD for 5-6 different flavors of Ubuntu and Xubuntu (some folks don't like the "DUNE" background) and all have booted into the Linux startup/intall screen. Give that a whirl and see what you get. So far, Ubuntu has been treating me, a recent convert from Windows, with kindness. Most problems have already been seen and there are them's willing to help out a newbie.
Oh yeah, burning at a slower speed than max improves the integrity of the image that is burned, but the last time that I burned, I couldn't change the speed from max.