I am having the same problem with my new ATT Radiant. z740, Android 4.1.2.
It did work out of the box but has since stopped connecting. Today, while on the road it did connect to Dairy Queen wifi.
My router is DIR 601 Dlink. Wireless N150 router.
I suppose I could do a factory reset, but if I have to do that each time I lose wifi connectivity , that just won't work.