Just in case, check these 2 links
http://www.dslreports.com/reviews/1596 http://www.dslreports.com/forum/cover,1596~days=365
How well is the ISP service running generally?
Now back to LW, go to LW's menu bar, Tools>Options>Advanced>Firewalls & change both connection & listening ports to one between 49152 - 65535. Try port 64049. Then close LW & re-open & see if there's any change. What model of Linksys do you have? It might be worth port forwarding. It seems port 6346 is blocked either by UPnP not working properly or by being blocked by the ISP. I know there's one range of Linksys models that don't work well /unreliable in UPnP mode, but all the other models are very good.
Also why do you have a Linksys? Was it provided to you by your ISP? I notice others are using Speedstream.