Cannot install 14.04LTS from USB startup disk

I am trying to install Ubuntu 14.04LTS from a USB startup disk. I used Ubuntu to create said startup disk. When I start the system, I get the pre-boot splash screen followed by the purple "press any key to continue" screen and then the Welcome screen. I can access the Help screens, but that is as far as I get; after I select "Install Ubuntu" -- or any other option for that matter -- the screen just goes black.

This is my platform:
https://www.asus.com/Commercial-Servers-Workstations/RS300E8PS4/
Motherboard Model P9D-C/4L / BIOS version 1301
8GB RAM / 128GB SSD (for Windows) / 500GB SATA HD (for Ubuntu)

I tried the USB stick on an old Dell Latitude D630 laptop and it worked just fine...although it did give a non-fatal ACPI error of some sort during boot-up. So I tried booting the ASUS server from the USB, this time hitting F6 at the Welcome screen and choosing "acpi off." Same result.

What else can I try?

Thanks for reading,
Les