Why does he only talk to me online and not in person?

It's so weird. We talk online, everyday. But he sees me at school, (we're in college) and he looks at me, but doesn't say hi, or anything at all. I'll try talking to him, and he doesn't look at me. I only ever see his back. I may say hi, and as he's walking away with his back turned to me, he'll say hi back, without looking at me, But on MSN, he's quite talkative.

We met on Facebook before our program started this year, we spoke quite a bit then too, and was planning on meeting up on the first day. It never happened.

I like him, but I'm afraid I'll scare him away, I don't know how to let someone like that know I like them without telling them straight and embarrassing myself. How can I get him to physically respond in a normal manner towards me?