Try deleting your LW Preferences folder whilst LW is closed; instructions here: Point #2 & 3 in Fixes for Limewire (sample image included at bottom of page.) For you Point #2 might apply.

hmm ... I presume you were able to connect with LW previously? Your newer internet connection type might be the issue.

It would be worth checking out this thread-post for tips If LW 4 Will Not Connect (click on the blue link)
such as replacing your gnutella.net file.