I am on JB and wifi is working for me. I have read that some are having problems and others are not.
A few speculations are that it seems to be related to older access points/routers and in some cases, updating the routers firmware helps.
First thing to try is reboot the router.
Are you able to connect to any wifi at all?
You can also try this. Go into WiFi settings and then hit the menu button again and choose advanced settings. In the advanced wifi settings screen, uncheck "avoid poor connections". That seems to help.