Okay, I've got two more things that came to my mind regarding your problem.
Firstly, I assume you see the brickwall in front of your globe in the left bottom corner of the LW window.
It is possible that this brickwall does not come from your (offline) firewall, but from your Antivirus program (in my case it was AVAST). I went into the menu of Avast and put the comeplete LW folder into my exception list. After that I restarted LW and the firewall dieappeared instantly. So, that might be a way to solve your problem.

Secondly, after reading some more about ISUnet, I came to this article:

http://www.isunet.net/support/support_disconnects.html

I don't know whether this is connected to your problem, but I thought I'd let you know anyway.....;)

I'm having dreadful connection problems at the moment. I get connected to LW bt often the connection drops and the connection quality display drops to next to nothing. Whe nI click on conncetions I see that all tge connections I had to Ultra Peers have died and LW is trying to connect to 3 more.

I've used LW for a long time and I know how to configure the program. This has only happened since LW upgraded to 4.12.3 and only in the last 12 hours.

The connection quality drops and then sometimes it goes back to full strength. Other times it drops to almost nothing, and when I click on the "Connections" tab it shows I have a connection to one ultrapeer with many more trying to connect. Twice I have had no connection at all, and then I get a popup dialogue box to say it was trying to connect, but after that, and regardless of what I do, I can't get a connection.

Help!

This is mightly confuzing...

plus I can no longer browse ANY host who is downloading from me...

Do you see a brickwall in front of the small globe in the bottom left corner of the LW window?
And who is your ISP?