Generic "my friends/users can't connect" checklist:
1) Are they connecting to your WAN address (
www.whatismyip.com)
2) Are the ports forwarded from your rotuer to the TeamSpeak Server on your LAN? (
www.portforward.com)
3) Have you made an exception for Inbound UDP traffic on port 8767 in your software firewall(s)? This includes the Windows Firewall which is ON by default in Windows XP SP2
4) Is the server running? (test by connecting to it yourself - localhost or 127.0.0.1)