It's not naive, but be careful. Not every guy on the Internet is looking to cheat on their significant other.It is entirely possible that he sees a kindred spirit who he's trying to give professional advice to. But that's the key -- keep it professional. If it starts to veer into territory that you feel uncomfortable with, cut off contact. Also, be upfront with your SO about who this guy is. If he asks, tell him he's a professional contact. As long as he keeps it professional and friendly, there's nothing to worry about.
Chic Geek
I agree! Sometimes it's great to have a sort of 'mentor' to share their professional experience with you and he probably feels good about being able to pass it on and be some use. But it's important that this relationship feels like that, maybe if you're starting to feel a bit uneasy about all the communication you're having it's a sign that perhaps you're unsure those roles are so clearly defined.