I have been unsuccessful when burning downloaded ISOs to a DVD on OSX - the burned DVD essentially has no content and the DVD is not bootable. I've tried Ubuntu versions of 11.x and 12.04 with no success. Further, I took the DVD out of an Ubuntu Unleashed book (v11.x), and am unable on several OSX laptops to read the DVD.
The applications to manage ISO disks on OSX are really straightforward, and they properly function with ISOs of other linux distributions. Is there a problem with Ubuntu's? Or is it just me?