Ubuntu segmentation fault

When ubuntu gave a "segmentation fault" (in my case something like: gave up waiting for root device), try to Reboot and hold down shift to get to the recovery menu. If you have some other kernel versions (olther ones) try them. If not, on the recovery menu select:

• fsck (hopefully that completes cleanly)
• enable networking (to allow downloads )
• dpkg (repair all packages)

After this I could boot up.
Perhaps this will help.