Did you check your Vista firewall settings to allow LW full access? User Cant Connect - LimeWire
Also check the sticky threads at top of Vista section of these forums.

Your router is an infamous one. It has firmware problems which Linksys never bothered to fix. Port forwarding is one fix, though it still may have some unreliable issues. The other is to fix the firmware yourself. There is a post on the forum about how to do that.

Well with such firewall issues, and you don't care about uploading? Well you will never be an ultrapeer, never be able to direct connect, and having less connections due to no uploads will mean less search & download results. It does make a difference.