Ubuntu 8.04 problem

Hello All,
Sorry, I thought the message below would give a clue to what is wrong without having to go into the full history.
Here it is from the beginning:

I received live cd's with Ubuntu 6.06/EMC2 and Ubuntu 8.04/EMC2 from Probotix, I tried running and installing 8.04 and it did not work, so I tried 6.06 which did not work with my onboard video but did install when I used an ATI PCI video card. Every thing ran fine until the update manager asked if I wanted to update to Ubuntu 8.04, I figured why not it should keep the configuration and should run. Of course I know now that the EMC is lost doing that, so I downloaded and ran the install script. When I tried running EMC2 it returned the message "EMC2 requires the real time kernel 2.6.24-16-rtai to run." I rebooted using the rtai kernel and got the Ubuntu progress bar for a long time, I walked away from the computer, when I returned I had the message detailed below on my screen.
Then I downloaded, did the checksum and burned the image of a new live cd from the EMC website,and Ubuntu 8.04.3 i386 and 8.04.3 amd64 from the Ubuntu website. The new live cd still did not work. Both versions of Ubuntu worked until I ran the EMC2 install script and tried booting the rtai kernel.
Now I stayed in front of the computer while waiting for it to boot the rtai kernel and found there was another message that preceded the one detailed below, and it was different for each way I tried to boot the system
.
Trying to run or install from the live cd with the ATI video card I received the following message:

vdevd-event [1285]: run-program: '/sbin/modprobe' abnormal exit

Trying to run or install from the live cd with the onboard video, I received the following message:

vdevd-event [1290]: run-program: '/sbin/modprobe' abnormal exit

Trying to boot the rtai kernel from the hard drive with the ATI card I received the following message:

vdevd-event [1277]: run-program: '/sbin/modprobe' abnormal exit


Trying to boot the rtai kernel from the hard drive with the onboard video I received the following message:

vdevd-event [1280]: run-program: '/sbin/modprobe' abnormal exit

I hope that this is enough information to solve the problem but not so much that it puts you all to sleep reading it!

Ray

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I tried installing EMC2 from the live cd and it failed. I installed Ubuntu 8.04 and it ran fine, but when I installed EMC2 and tried booting the rtai kernel I received this message:

Loading, please wait...
check root = bootarg cat /proc/cmdline or missing modules, devices : cat/proc/modules ls/dev
ALERT! /dev/disk/by-uuid/04305177-f75e-4da0-8f56-f258c89ba7db does not exist. Dropping to shell!

I know nothing about Linux, is there any chance someone can explain how to fix this problem?