Wtf just happened? I came in here to help you solve your problem and what do I find when I enter your thread? No problem at all! Instead, you even post the solution immediately after your state what the problem WAS! I was so disappointed.
However, I visited your thread via the forum live feed on the homepage and NOW I realize that we're in General Discussion. You fooled me again, twice in the same thread, with just one post.
Well played, Sir. Well played indeed.
On another note though, you can always set USB flash drives as a lower boot priority then your HDD if you don't want to fall victim to this scenario again. If you ever mean to boot into a USB flash drive, you'll be much more aware to change the boot priority to reflect that than if you ever forget you have a flash drive in plugged in when you boot.