My ipad is conecting the wifi but after few minuts it stops data transfer

Dear

I have an Ipad2 64 GBing since 10 months, recently updated firmware to IOS6, after that I am not able to have a sustainable data connetion through wifi it ays shows conected to networ. but I coud not download or brows internet.

I have done factory defacult formating and resetted network, but still not working.