Context: rEFIt 0.14 with kubuntu 10.04 on a duo Mac Mini, triple boot with Mac OSX, kubuntu, WindowsXP.
Setup essentially that suggested by firstname.lastname@example.org, whose instructions work perfectly with (say) kubuntu 9.04 using GRUB.
With a GRUB2 loader in the partition, there are various weird effects of some icons booting and others not, or booting apparently
the wrong system, and interacting with the stage1 loader in the MBR. I believe all of these can be traced to a failure to boot
from a GRUB2 partition. In attempting to fix this on the mistaken impression that the trouble is in GRUB, the MBR and partition
boot records get messed about, leading to other weird effects. (It has also been suggested that an ext4 (instead of ext3) file system
may be at fault, but I haven't investigated that. One gets tired of re-installation...)
It is a work-around for creating a ubuntu 10.04 system to add a spurious extra Linux partition at the end (beyond the four
of the MBR partition table, put a GRUB system (say kubuntu 9.04) there, with its loader on the partition, not the MBR,
then use the "boot" program to copy the GRUB loader from this spurious partition to the others that won't boot. The
drawback is that all the GRUB control files reside in the spurious partition, which must be maintained. (rEFIt can, however,
boot to it.)