Is it your wifi? Certain combinations of Linux wireless driver + router security don’t play well together, rare nowadays but you might be unlucky. I’ve got a wireless USB stick with this problem.
Try (temporarily) an open wifi network to see if it works, and if it does then try some different encryption settings until you get one that works.
If it’s not your wifi, then try another distribution (Fedora, OpenSUSE…) on a live CD to see if you get any luck that way.
EDIT: Crossposted with funkynick