This is cross-post from ubuntuforums.org but as I've received no responses there I'm hoping for better luck here.
Basically, I've installed the full version of Ubuntu 12.04.2 LTS on a 32 GB SanDisk Extreme USB flash drive using both the 32- and 64-bit live CDs on my Lenovo ThinkPad T520. The installation completes successfully with no issues, and I can see the USB drive in my boot menu under "ubuntu", but when I select it and hit "Enter" the boot menu simply reloads.
It seems like, while the machine can clearly boot Ubuntu, there's something about using a USB flash drive that prevents it from working. I've found references to an issue with ThinkPads, but I'm not sure if it's relevant or how to implement the solution.
Additionally, I've run Boot-Repair to no avail (the results can be found here - sda is my internal HDD (Windows data drive), sdb is an mSATA SSD (Windows system drive), and sdc is the USB flash drive).
Any help would be greatly appreciated, thanks!