It’s your router. Most Linksys routers do this. I’ve had to help out my friends constantly with theirs.
1. Go to http://192.168.1.1 and put “admin” for password. and login.
2. Go to Applications & Gaming at the top.
3. Make a new entry and put AIM. Ports: 5190-5193. Protocol: TCP.
4. To find out your IP Address. Go to Start > Run > ipconfig .. and it will tell you there. just add the last 3 numbers of it into the last box in the Applications & Gaming.
That should fix everything. if it works, let me know by IMing me @ notastud231