For the past several months, our support forums have been plagued on and off with a number of weird and inexplicable failed attempts at installing Ubuntu by many users. Ubuntu (ever since version 5.04 Hoary Hedgehog) will not install properly on a filesystem other than ext2fs or ext3fs.
Read about it in this post
Unfortunately if you attempt to install Ubuntu with the “/” partition formatted as ReiserFS, JFS, XFS or any other non-standard filesystem, Ubuntu installation will begin like normal and tick merrily along its way until it attempts to install GRUB. At that point, you'll get a fairly inexplicable and non-verbose “fatal error” message about “grub-install()” failing.