Okay, so I'm really unsure what the problem is with my Macbook.
I run on leopard and have never had any troubles with any applications, ports or firewall issues.
So my issue is such: I have been trying to run two certain apps on my computer (Second Life and Limewire) and neither of them work.
On my Limewire it is unable to connect and the firewall blocker appears in the bottom left window. My roomate, who is a Second Life user as well is able to connect to her application fine and we are under the same wireless connection.
So I went into my system preferences and went under Security and into my firewall.
Being OS X, it gives me a number of selections: general, filevault and firewall.
Under my firewall settings I can put it under 'all incoming connections', 'essential services' and then 'select applications'.
For now I am under the select 'applications options' which enables my Limewire and Second Life applications to function-but they DONT.
I have no idea why this is happening and I am even unsure if it is a firewall issue. I have wireless internet fine, my itunes is able to connect to the store and I seem to have no other issues.

The only thing I can think of that I have changed on my Macbook is:
-changing the port # for ichat
-downloading PeerGuardian
-downloading the new (******) version of Limewire
-re-downloading and older version of Limewire

Thanks for reading, hope to hear from anyone!!!