Installation problems for Linux guest OS

I downloaded the free trial for Linux yesterday. I had no problem installing it in my Ubuntu 9.04 OS. I was able to create a WinXP VM with no problem either. However, when I tried to create a Ubuntu 9.04 VM, I ran into a problem. Following the documentation, I configured the DVDROM to load from the ISO image that I had. It would reboot the VM and then the boot image was not found on the DVD even though it was there.

I also tried the bootable version of Ubuntu, where it did start the boot process and I got the boot menu. Even though I could navigate around this boot menu within Ubuntu, when I'd press enter on the 'Install Ubuntu' option, it would do nothing. I could not figure out how to install the Ubuntu VM, withing the host Ubuntu OS.

I'm running an i7 920, 4GB DDR3, 2TB hardrive, so it should far exceed the system requirements.