LW 4 has had problems in recent times when using old gnutella.net files to find hosts to connect to. LW 5 can find them automatically if it does not have such a file initially. So installing LW 5 may have updated the gnutella.net file with 'good' recent hosts to connect to.
This is my guess at least.
We do offer an update for the gnutella.net file at the bottom of this post
If LW 4 Will Not Connect (click on the blue link). However you will not need that now.
But .. you now know that if you install LW 4 again on a fresh computer, you will most likely need a 'fresh' newer gnutella.net file to add to it.