I am new to rooting etc, and have followed all of your steps, however I am now stuck with the M logo and the DUAL CORE TECHNOLOGY badge central screen.
My Xoom is a UK 3G Xoom, MZ601. I successfully unlocked the bootloader, connected with adb, then flashed the recovery-tiamat-r4c-100611-1150-cwm image.
I also successfully entered recovery mode and chose to install the xoom-universal-root.zip file I downloaded from this post.
Now I always get stuck at the M logo when trying to boot. It will still boot into recovery mode if you can give me some help as to what I should do from here.