I also want to chime in and say this exact thing is happening to me.
It started after the latest system update. When I go to the internet browser so I can log into the WiFi that way, the browser says "The Internet browser cannot be used at this time. Please check your network environment or try again later."
I was able to connect to the WiFi via the browser before the update, and now I no longer can. U: I don't know if the DS would work with a regular WiFi connection as the connection I'm trying to use is the one we have at home, but from what I've seen so far, it seems to be affecting people's connections that have to enter a password first in an internet browser before they can use the internet. :/