I need to know if it is possible for any user to get onto an Invasion Power Board forum and get IP addresses from members? I've got a member who swears up and down that it is possible and wants me to delete all 5000 posts to keep it from happening.
The IP addresses are stored in your MySQL database, that's the first thing you'll want to make sure is secure. You should make sure your version is up to date, and you should change your password just in case, make it something random like j2b9jahr3u3e
Next you'll want to ensure that he doesn't know any of the administrators passwords... check your admin logs at your invision board to see that no foreign people have logged in recently, ask your admins / anyone who has access to view IPS on the forum to update their passwords if you want to be safe...
Backup your forum, and then be on with your day, don't even bother replying to that guy, ban his account if he's a member at your forum.
Just giving you some ideas, there's no widely known security flaw like he's pounding on his chest and yelling at you, he's most likely bluffing, but you're better safe then sorry.