Ubuntu is installed on a 32 gigabyte flash-drive and it successfully booted every time up until I partitioned my hard-drive and installed Windows as a secondary boot (for programming reasons). Now every time I attempt to boot the Ubuntu flash-drive it boots into Windows XP. The same goes for partitions, I partitioned my hard-drive and installed Ubuntu and it only booted Windows XP.
I am on a MacBook 6,1 with Mac OS X 10.6.8, 2 partitions, and I am using ReFit as my boot-loader.
EDIT: I had Ubuntu working fine from FLASH DRIVE and at one point as a partition. I later uninstalled Ubuntu from my hard-drive and installed Windows. I then had to re-image my computer for certain reasons and I installed windows. Now when I attempt to boot anything other than Windows or OS X it boots into windows.
Ubuntu was never on my hard drive while Ubuntu was on it. The flash-drive has been its own thing and has the boot-loader installed to it and loads from ReFit but boots into windows.