Comment 18 for bug 990913

Same for me.
System: Supermicro X9SCL-f CPU XEON E31220 RAM 16GB ECC 2xAdaptec 1430SA with 7xWD20EARS md-RAID5

Nearly every reboot ends in an degraded RAID with initramfs Prompt. Resuming boot apears good.
It seems to me a timing problem loading the needed modules.
So for my system helps:
/etc/initramfs-tools/initramfs.conf:
-MODULES=most
+MODULES=dep

or

-MODULES=most
+MODULES=list

with

/etc/initramfs-tools/modules:
async_xor
async_pq
async_memcpy
async_raid6_recov
raid6_pq
async_tx
raid456

Don't forget to run mkinitramfs:
 mkinitramfs -o /boot/initrd.img-{version} {version}
with actual version (3.2.0-24-generic) for me.

Hope this helps ^^