I hate to open up a new thread because I know there's an answer out there but I was unsuccessful in searching for it.
I keep failing to install a fresh Mint (no dual-boot whatsoever) via USB and I'm not sure what exactly is the problem but I'm guessing making USB bootable is where it fails.
Like suggested, I format my USB stick (8 gigs) to FAT32 (although I've also tried FAT16 with diskpart), run the Universal USB Installer, select Mint 14 (md5 matches) and browse to the latest mint cinnamon iso, select the usb drive and hit next and wait it out. Supposedly it finishes successfully but when I restart my PC, hit F12 and try to boot from usb-hdd it either doesn't recognize it, or I get the "no default or UI configuration directive found" error. If it counts for anything, I didn't have problems with Windows installations from USB, so I guess I shouldn't have problems with booting Linux installation from USB either, but I'm not sure.