Okay, so I'm told that, in order to play DS games online, you need a connection with either WEP security or no security. My home connection has WPA security. I'm by no means an expert on this stuff, but I understand that WPA is more advanced than WEP and that DS games cannot be played online with a WPA connection.
Cue my next door neighbour, who has a connection with no security.
I can connect to said connection completely fine on this netbook. I can even connect to said connection under the DSi's "advanced setup" (connection "profiles" 4-6, which also work with my WPA connection). However, I cannot connect to the same connection with the default connection (connection "profiles" 1-3), which are the ones on which DS games are played. Yet to the best of my understanding, connections 1-3 are supposed to be compatible with no-security connections.
Sorry, man. I really don't know what to do to help you. I'm having troubles with my DSi, myself -- it's suddenly decided that it can't connect to the internet at all, and it can't even detect unsecured connections that I know are there.
I've heard it said that the wireless capabilities in them kinda fail after a few years thanks to planned obsolesence, so I'm a little nervous that mine's never going to be able to connect again due to something failing/breaking down/just plain breaking/whatever.
So much for filling up my Pokedex.
Though, now that I think about it, I seem to recall hearing that though the games themselves won't connect with WPA security, the DSi itself is actually perfectly capable of connecting to WPA security. The games just don't have support to connect, and need WEP or nothing... but I guess that doesn't help you very much, other than to confirm that your wireless capabilities still work, period. Well, I hope somebody can help you fix your problem, anyway! I'm sorry I couldn't offer you anything useful...
But that's the thing. It ISN'T complicated. I can connect to said connection perfectly fine on DSi connection profiles 4-6, but I can't connect to it on DSi connection profiles 1-3 (the ones that games are played on).
That's just it. Nintendo dug themselves in a hole with this whole 6 connection profile crap when they should have just done the work and supported all encryptions from the start so things actually work.
Instead of..you know...assuming people would want to sacrifice their security and livelihood just so they can play games with little to no security. If you didn't know, WEP can be hacked by an infant with one of many packet sniffers and injectors.