I had this WiFi Authentication problem on my android tablet til yesterday. Sollution --> login to your router, go to advanced WLAN settings, change channel from auto (or if a static nr is set change it, try another) to channel 1, 6 or 11. I changed in my router from auto to channel 1 (if ch1 do not help you, try any other ch) and my lenovo android tablet stopped behaving this "god-damn-annoying" "WiFi Authentication problem" way.