It's just odd that you're getting those great d/l speeds and bad upload speeds. Are there any peers on that particular torrent? Or a really low number of them? If there are 15 seeds and only one peer, then all 15 seeds are sending bits to the 1 peer, so your speed will be pretty low.
If that's not the case then I'm really not sure. You're getting the NAT error so...
Also check your wireless's website. They very well could have some helpful info about this. There most likely is a firewall built in, since it's a router.
Assuming you don't have a firewall, though, before you go nuts looking through everything on their site, plug in your local IP where it asks for it and see what happens. Again, since you're on a network, that number will most likely be 192.168.0.X where X is the number your computer is on the network. If you don't know that just plug in 0 and try, then 1,2 and 3. If none of those work, see if you can get your real IP (from that site I linked or google for an IP finder) and try that.
Then I'd say plow through the manufacturer's site.
Sorry, I wish I could be more helpful. I know it can get frustrating, trust me.
