DS Lite crashing when trying to go online.

I have asked the same question on a different forum , so I´ll just C&P it:
"I recently got a router and a new ISP. I configured the WLAN connection on both my router and NDS, and the connection test on the handheld gives me an ok. The problem is: Whenever I try connecting to the WFC Network , my Lite "crashes", meaning the screen freezes and nothing happens.
It worked fine with my brother´s router.

I´m using a Zyxel 660HW , a router provided by the ISP called Arcor (which some German members might be familiar with).

Halp plz "

Yeah so... help please :P .

What game are you trying to go online with?

It´s not game specific, it happens whenever I try to establish a connection. (also with any kind of homebrew that uses wifi)

Hm...thats weird...never heard of that happen before, see if you can try connecting on a few more routers, if they all connect fine then it's probably something messed up in the router, try disabling WEP if you have it enabled also or changing the wireless channel