Well thats because bootcamp isn't built to support Linux. It's only written to run Windows. From Wikipedia:
Linux is not supported by Boot Camp, but some distributions ship proprietary drivers to achieve partial compatibility with Apple computers, with various small problems occurring, such as reduced sound output quality, and numerous issues with MacBooks and hardware sleep.
If your only out to try it: you could use Parallels and run Ubuntu inside of Mac OS X. It's not the same thing I know but it's an excellent way to get a feel for the operating system and if it's worth installing and a physical machine. I do this all the time.
And reine: as long as its Linux - I really don't care what distribution it is and nether should you. Were all part of the the same community