I have found this to be a consistent problem but have found no hint on resolving it online. Whenever I race over WiFi, I get through 3 courses and my DS locks up/loses its WiFi connection just before the countdown for the fourth race. Anyone have an idea why it would lose its connection in that exact spot each time? I'd like to finish a full Grand Prix sometime!

Well, if you plan on getting any help you need to say some more details. Like what router are you using. Try nintendowifi.com and go to the forums as they have a lot of info for specific routers.

I am using an SMC Barricade g which Nintendo rates as fully compatible.

You might need to change your Tx rates (transmission). The DS is designed to communicate at either 1 or 2 mb/s. Try setting it to that.

Thanks! That worked. Kinda sucks that I have to force all wireless connections at home down to 2mb/s just to play Mario Kart. I wonder why the "auto adjust rate" setting only works for part of the time. Maybe I need to extend another setting to like 30 minutes before the router forces "renewing" a connection...

actually you should probably check to see if port triggering or forwarding is on and if it has a time limit on the port. it is common for routers to do this and after 15 to 30 min depending on the maker you get dropped from a game or video chat etc. anything that isn't using the standard ports i.e. 80,21,etc.