Normally, routers should not lock up under load.
Could you check on your router constructir's site if your firmware is up to date ?
Do you have a Norton auto-protect or equivalent protection software enabled ?

On the other side, some friends using emule/kaaza/.. behind some VoDSL router have report thet their router powers off due to the excessive number of connections their p2p soft make

In my case: LW -> Airport -> DLINK 1000 AccessPoint -> VoDSL router -> Web, I never face any problem.

Phil