Sometimes dmraid finds metadata when it shouldn't (either because of previous uses of dmraid, or because of a bug). Have you tried booting with the 'nodmraid' option? It's on the F6 menu on the live CD because some people need this.
Your syslog confirms this: Mar 20 20:54:59 ubuntu activate-dmraid: Serial ATA RAID disk(s) detected. If this was bad, boot with 'nodmraid'. -- Ubiquity can't find the sata hard disk (promise 376 chip) https://bugs.launchpad.net/bugs/543008 You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
