6.1 install on a PowerEdge 6400 with AMR raid card

I found this problem on an archive of this list.
http://groups.google.com/group/mailing.freebsd.current/browse_thread/thread/c6227c003f6817df/c720a6c7a55c807a%23c720a6c7a55c807a

This is very similar to the problem I'm having with my 6.1 install.  I
set up a raid5 on my AMR card (an enterprise 1200 with 4 scsi discs)
and booted up the installer.  After partitioning the disks and
labeling, choosing distributions, etc.  I hit commit and it reliably
stalled after adding part 2/30 from base.  Strange behaviour, I
thought.

So I got around this by booting up with Freesbie and using that
sysinstall after changing it to install 6.1-RELEASE but otherwise with
the same steps all the way through.  It worked well and I rebooted.
And the OS wouldn't boot (some error regarding LBA).  Trying to boot
with grub also showed an error of similar sorts.

It came to me that it may be the raid5 that was at fault for the
booting issues so I quickly (as quickly as one can, at least) set the
disks up in a raid10 and installed freebsd, but upon trying to do
mountroot, it hangs leaving a mountroot prompt that cannot be typed
into.

Are there known issues with the MegaRaid Enterprise 1200 cards for
booting FreeBSD?  Are the passingly-mentioned patches already in the
6.1 tree?  Does anyone have any recommendations of things that can be
tried before I purchase another RAID card?

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