The DG814 is really the worst ADSL modem/router you could possibly ever own, I know because I have owned one since they were released. The router crashes when you generate lots of UDP traffic (like you describe), and you have to manually reboot the thing. You will find the same thing happening every time you try anything really UDP intensive - like EDonkey, or Overnet stuff.
This will never be fixed, I have been in contact with Netgear support for ages, had new routers, all the Beta firmware releases and nothing fixes the basic fault. The fact of the matter is that the router is just not up to the job.
If you can limit the amount of UDP you are generating it might crash less often. For example, I use ASE to find servers, and you can limit the number of packets it sends per second when you scan servers.
The only long term fix is to get another modem/router box (I have used DLink boxes without any problems), and never to buy anything from Netgear ever again. Which is a shame, as all the stuff I bought from them before was cool.