Same problem here (dual Opteron 246 on Asus K8N-DL with 2 120gig SATA in RAID0 configuration). It looks like this breaks any raid configuration depending on dmraid - not only to boot from RAID, but also to simply mount and access existing arrays. I'd think the latest version of dmraid should probably be included in repositories as soon as possible.
** Changed in: Ubuntu Status: Unconfirmed => Confirmed -- DMRAID stopped to work in kernels > 2.6.15 https://launchpad.net/bugs/54246 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs