Why is it that when I download Bittorrent, my router freezes?

"Bit torrent clients typically either saturate the upstream traffic of the internet connection or use up more connections that windows allows.

Try configuring your bit torrent software to have a maximum upload speed. I have a cable modem and I limit it to 20-40 KB/s, depending on what I'm doing on my computer otherwise. You'll have to fiddle with your settings to get it working correctly for you.

Be aware there are multiple factors you need to consider

the quality of your router (i found downloading many torrents would often cause my netgear router to overheat, so i kinda had to queue my torrents)
what other things you're using (listening to internet radio, watching hulu or youtube, VPN into work, etc etc) the more connections you have going on, the less there are available for BT. This applies to your whole home network, just not what you're doing on that one machine.
your windows configuration (hope many connections you're allowed to make, typically changed by messing the the registry... i personally try to stay away from doing this)"

Aside from what's been said above, there is another glaring possibility: buggy router firmware, that's crashing on some packet that is rarely seen outside of P2P protocols. Try upgrading the firmware. If not, replace the router with a better one. Drayteks are pretty good as SOHO routers go, but you'll pay for them.

"Bittorrent automatically adapts to blocked ports/NATs and while it may saturate your uplink, it shouldn't completely prevent other connections.

Does the bittorrent download start properly or does the router stop responding as soon as the .torrent file is downloaded? If it's the former, then limiting your upload speed from the bittorrent client should help.

If it's the latter, your router is trying to block bittorrent traffic. Try connecting an another computer to your network. If both computers' Internet connection freezes when you click on a .torrent file on one computer, the router is probably trying to do layer 7 filtering, fails to parse the traffic and freezes. In this case, downloading and installing a firmware update for the router should help.

If only the Internet connection for the computer that tried to download the .torrent freezes, then the filtering is working properly and you should be able to disable it from your router's settings. What is the make/model of your router?"

"Check the maximum number of concurrent connections that your router supports: The router I use has an upper limit on the number of concurrent connections (255), so when I fired up Bittorrent for the first time (a few years ago), I couldn't use my phone anymore (voip).

Limiting the number of connections in my bittorrent client helped me there."