I think something is wrong with Mint 17.
That is quite a leap, I think what you meant to say is that 'you' could not get it to boot. Several days ago, I downloaded Linux Mint. I decided to put it on a flash drive and used unetbootin to do so. 15 minutes later, I was booted into the Linux Mint on the flash so it is not just Mint. Your post does not include any info on your hardware or the method you used to create the flash drive nor do you nor specifics on what happens when you try to boot.
I don't understand your comment about the Log In window. Since you indicate you can't boot from the flash drive, where are you getting a log in window?