Comment 6 for bug 561390

I am experiencing exactly the same problem since I upgraded to Lucid two days ago.

Seems to be related to the following issue in Lucid:
https://bugs.launchpad.net/ubuntu/+source/mountall/+bug/527666

The boot process hangs with the following message:
The disk drive for /xxx is not ready yet or not present.
Continue to wait; or Press S to skip mount or M for manual recover

/xxx is any partition on LVM.

I have to execute the following procedure to get to the GDM screen:
1. Enter M (for Manual Recovery)
2. Execute "mount -a" which mounts all filesystems on LVM without problems.
3. CTRL-D to close the shell and continue with the reboot.

Check the bug report mentioned above for detailed information on the issue.