What should I do about a clingy fan?

Sorry this question is so long, but please bear with me.

I'm not going to name him/her, but I was talking to a seemingly nice and normal Fanpopper for a while. Then, his/her messages started getting weird and making me uncomfortable, and it seemed like s/he was making things up. I know he/she has been lying to other users as well, so I decided to block him/her without their knowing.

Recently, he/she posted a personal message to me on a forum post of mine, which I promptly reported. Now, it's like I fear running into this person on the clubs we have in common, and some of the things s/he says there make me uncomfortable, not knowing if s/he is joking or not. Not to mention, s/he has found my YouTube account.

Should I report this user, politely ask them to stop bothering me (which I doubt will work), or something else? I'm getting pretty desperate and may resort to quitting Fanpop and YouTube. Or perhaps I'm just overreacting?