I helped my friend update his Dell precision T3500 from Ubuntu 10.04 to 10.10 today. After reboot, the system stopped and left me the following message

udevd-word[169]: '/sbin/modprobe -bv pci:v00008086d00002822sv00001028sd00000293bc01sc04i00' unexpected exit with status 0x0009

Gave up waiting for root device. Common problems:
 - Boot args (cat /proc/cmdline)
   - Check rootdelay= (did the system wait long enough?)
   - Check root= (did the system wait for the right device?)
 - Missing modules (cat /proc/modules; ls /dev)
ALERT: /dev/disk/by-uuid/.....(a uuid here)..... does not exist.
Dropping to a shell!

BusyBox v1.15.3 (Ubuntu 1:1.15.3-1ubuntu5) built-in shell (ash)

(initramfs)

After some googling, I finally found this post as a workaround which worked for me. #35 in that post gives a detailed instruction.
The basic idea is to give "pci=nocrs" option to the kernel.
I sum up the instructions here.
Boot from previous working kernel, then backup grub files

$ sudo cp /boot/grub/grub.cfg /boot/grub/grub.cfg.orig
$ sudo cp /etc/default/grub /etc/default/grub.orig

Edit file grub

$ sudo vi /etc/default/grub

Find and edit GRUB_CMDLINE_LINUX line like this

GRUB_CMDLINE_LINUX="pci=nocrs"

Update grub

$ sudo update_grub

Then reboot and enjoy 10.10.