I did log out and back in, same problem, and the skill remains. Very frustrating.....

I am trying to unlearn treasure hunting for Investigation. When i hit the small X to unlearn it, it resets it to 0, but doesn't make the skill disappear. When I hit the X after its at 0, it says "Unknown Crew Skill" in the chat window yet still appears in the skills window. I am unable to learn something new now, is this a bug or am I doing something wrong?? Please help... Thanks