I'm using BlackICE PC Protection 3.5 and it keeps reporting that it's blocking thousands of TCP port probes. I also see in the connections tab for limewire that I'm running as an Ultrapeer and I have many incoming hosts connected to me with the Leaf protocol.

Is my firewall (BlackICE) preventing users from connecting to me as clients? Should I tell my firewall to open 6346 (the port that Limewire options says it listens to). Is my firewall hindering Limewire from being an Ultrapeer?

I'm fairly certain this has nothing to do with Forcing IP, since that concerns to port forwarding through an IP masquerading machine.

First off, let me start out by saying that I've never been an ultrapeer so I don't know what it looks like. However, it sounds to me like if you're already receiving connections from leaf nodes your firewall seems to be allowing your machine to function successfully as an ultrapeer.

As for BlackICE blocking port probes, I'd offer some theories, but they're certain to be wrong.

BlackIce only prohibits unsolicited information. If you are running LimeWire, it isn't exactly unsolicited. It won't prohibit any information passing from your computer. Look up the references to a push. Try a standard firewall leak test on it and it will fail.

If you want more information on firewall vulnerabilities check out these sites:

http://rr.sans.org/firewall/not_enough.php

http://grc.com/lt/leaktest.htm

All this came to light when GRC came under attack. They discribe it here but I have to warn you, it's lengthy.

http://grc.com/dos/grcdos.htm

Anyway, because you have limewire installed on your pc, it allows others to contact because they become "requested" information.

Yes, LimeWire is a true potential security threat along with most programs you install. (although limewire distrubes it's code so you could discern what it actually does, but I'm as likely to do that as carefully read licensing agreements)