When the initial start screen of Ubuntu appears where you can chose to run the Live-CD, test the RAM and so on, mark the Live-CD-option and press
F6.
Then a text line appears which shows the kernel with it's options that will be called.
At the end of the line you will notice two parameters called
quiet and
splash. Remove them and press
Enter to see error messages while Ubuntu boots and post these messages here.
Most likely it will work if you add the parameters
noacpi and
noapic to this line. Try it!
If Ubuntu still doesn't boot try
Kanotix or
Sidux instead.