Eh, if you have one of those old routers, if you have a wide range of ports open, the routers will act gay like that. Don't know how, don't know why, it just does. If you do, close the ports and open open the needed.
Edit: Just checked the rest of your post. And I have the exact same router, even down to the firmware. Up to a week ago I had the same problem, I didn't have it before. Once I start torrents, I cant do anything else except let uTorrent run. It got decent speeds but nothing else, no internet/can't access router etc etc.
I also had to reset my router after I finished downloading to kickstart my internet again. The only different I could think of about 2 months ago when my uTorrent and router weren't gay till up to 2 weeks ago when its all gay is that I had opened "alot" of ports for Command And Conquer 3: Tiberium Wars. Once I closed em, everything was normal again.