grub fails on RAID

Hi again.

I'm trying to install 12.04 in a PC with RAID (ICH10R) but it nearly impossible.
I already submitted bug #990744 because the Ubuntu installer can't create swap partition. Eraserix suggested not use any swap as a workaround, and I did it. But at the end of installation grub fails with the message "grub-installer: error: Running 'grub-install --no-floppy --force "/dev/sda"' failed."
The problem is it must be installed in /dev/mapper/isw_bajfdgcbgf_Sistema which is the RAID set. A window pops up asking me to select another device, to continue without grub, or to cancel the installation. I double check the /dev/mapper/isw_bajfdgcbgf_Sistema thing is selected and click ok button and it fails again: grub-installer: error: Running 'grub-install --no-floppy --force "(hd0)"' failed
It happens that I don't have a IDE disk or DVD device plugged in my PC!

I also choose continue without a boot loader and used my 10.10 install to update grub entries. Then I rebooted the computer and choose 12.04 to boot, but the boot process stops at initframs or something. I can type help to see commands but I really don't have any idea to what to do.

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: ubiquity 2.10.16
ProcVersionSignature: Ubuntu 3.2.0-23.36-generic 3.2.14
Uname: Linux 3.2.0-23-generic x86_64
ApportVersion: 2.0.1-0ubuntu5
Architecture: amd64
CasperVersion: 1.315
Date: Thu May 10 23:02:14 2012
InstallCmdLine: noprompt cdrom-detect/try-usb=true file=/cdrom/preseed/ubuntu.seed boot=casper initrd=/casper/initrd.lz quiet splash -- maybe-ubiquity
LiveMediaBuild: Ubuntu 12.04 LTS "Precise Pangolin" - Release amd64 (20120425)
ProcEnviron:
 LANGUAGE=pt_BR.UTF-8
 TERM=unknown
 PATH=(custom, no user)
 LANG=pt_BR.UTF-8
 SHELL=/bin/bash
SourcePackage: grub-installer
UpgradeStatus: No upgrade log present (probably fresh install)