I don't think the LW 4.0 was UPnP capable. I'd need to check. If that's the case you will need to port forward your router. I had a similar version.
You will need to set up a static ip first: Computing & Information Technology : University of Vermont
Then see http://www.gnutellaforums.com/connec...4g-router.html which should be similar to yours.

If LW was working fine before then try deleting the LW prefs folder whilst the program is closed; found here: Macintosh HD/System Folder/Preferences/.limewire
List your prefs folder in List mode & you should find it at the top.

Thanks for your help.

I'd already tried deleting prefs while closed (more than once...in case it didn't take the first time ).

The thing that doesn't make sense to me is that I've used LW for years now with this set-up (whatever UPnP is), why would there be problems all of a sudden do you think?

I'll look into the port forwarding stuff now & let you know how I go.

EDIT: No luck with the port forwarding.

Any other suggestions? *crosses fingers*