im quite familiar with shoutcast, i might be able to help, i think that you probbably have shoutcast set up using the same ports as http, as in port 80, that might be the problem, you probbably messed with the settings since shoutcast uses port 8000, you might have erased the last two zeros off of there.
try uninstalling and installing it again, that might return it to it's normal settings.
hope this helps
EDIT: Also make sure you have the ports open so people out side your LAN, can access it.