why my iphone 4s cannot connected to wifi after upgrade to ios 6.1.3

Settings/General/Reset - Reset Network Settings. If you can't turn WiFi on see: http://support.apple.com/kb/TS1559

I did this "fix" and it worked...for awhile. Wifi went out again and is now greyed out and none of the suggested work abounds are working now. I hope that Apple corrects this soon!!!