First, would like to point to two references:http://laptop.org/8.2.0/manual/
The manual, in the nework section, has some good guidance.
The details are in:http://wiki.laptop.org/go/Wifi_connectivity
The first simple thing to try is to reset the Network history (and restart). Make sure you know any security keys for other sites.
The next is to reset your access point / router to factory defaults (make sure you know the parameters to re-enter after the reset) and then re-enter the parameters. There is generally a reset switch somewhere.
These are to assure nothing has become corrupted.
Finally, have you changed anything on you primary router, such as MAC filters ?
More detailed suggestions are in the references.
The wireless test programs are in /sbin and begin with iw* . Run them with the help option. These are general linux programs and not all work on the XO.