Samsung Galaxy S3 WiFi authentication error with A&TT U-Verse router
Easy fix.  Don't use your wi-fi password.  Use the Wireless Key #.  I have been trying over and over with my personal password and kept getting the same authentication errors everyone has been discussing with u-verse.  I pulled the paperwork that the installation guy gave me and just taking a last resort shot at it, I tried the Wireless Key # written on the paperwork.  It connected immediatley... 

This reportedly also works with the Verizon branded Samsung Galaxy S III. Their 2nd level support only suggests factory resetting which won't help. Only the above mentioned technique does