[U2Lynne]

If you are using Win XP or you use a router, then you are most likely firewalled and so you need to forward your ports so you can 'see' everyone. If you are firewalled, then you can only see people who are not firewalled and you can't see anyone else who is also firewalled. This limits the people you can upload to (and also the people you can download from). There is a link in my sig for forwarding your ports from your Win XP firewall and then to forward your ports through your router, get the router make and model and head over to portforward.com and follow their instructions on how to forward your ports.

Whoops, nix the part about a Win XP firewall. For the Mac, look in System Preferences > Sharing > Firewall and either Stop your Firewall (I think by default it is off, so you may not need to worry about it), or if you wish to keep it on, create a New 'Rule' : Port Name/Other, TCP Port Numbers/6881-6889 (or whatever they tell you at portforward.com ), same with UDP Port Numbers, and Description/BitTorrent and Save and put a check mark next to that Description.