I find the gnutella.net file seems to go stale fairly quickly with LW 4.16.6. I do also run LW 5 in a different account, so I swap the gnutella.net file across (whilst LW is closed) & it connects again.
Glad to hear you at least found a solution of sorts, similar to my occasional one actually.

But not really a totally happy permanent solution. Likewise, last several times I tried, my OS 9 LW connected well.
LW developers recognised the connection issue with LW and put in a function of a kind of self seeking for fresh active ultrapeers. Unfortunately they only discovered this issue after LW 5 was released & refuse to update the issue for LW 4.
Edit: you may wish to consider copying your OS 9 LW gnutella.net to your other OSX LW preferences folder & replacing the OSX one.