Huge problem here involves a Dlink router

well im having a big problem. When ever i download off of p2p programs my internet goes down. But when i download off mirc and torrents it doesnt. I dont know what the hell is going on here. My ISP say they wont fix the problem cause downloading is illegal but everyone that is under the ISP i have theres never goes down. So its got to be something with the router. My model is a [bold]D-Link DSL-604t[/bold]. My one friend said it could be firmware but he couldnt find me any for it so i dunno. IF someone could fix this problem i would be more then happy. Thx in advance.