Many Vista users have had problems with LW & McAfee...have a read thru these.
Vista + McAfee 2007 + LimeWire = dropping connection “No Compromise” Vista-McAfee-Limewire Solution Can't Connect With VISTA!
When you set up port forwarding, did you set up a static IP address first?
What version of Java are you using?
Who is your ISP?
Have you tried any other p2p apps & if so, do they work properly?
If you're connected as a leaf, you'll connect to ultrapeers. If you're connected as an ultrapeer, then you'll connect to peers (other ultrapeers) & leafs.