I had this happen to me a few weeks ago with no explanation (no I'm not a minor). When I attempted to check in online, it wouldn't let me, so since I didn't have any checked baggage, I thought I could quickly get a boarding pass at a kiosk at the airport. Instead I got the "special handling" message. When I went to the desk, it took the agent about 15 minutes to finally get a boarding pass. When I got to the gate, the same thing happened, and I had another 15 minutes of waiting while they straightened it out. I never got an explanation as to what was wrong. It's times like this that I'm glad that I always give myself a lot of extra time at the airport.