Try a hard reset of your system ...
1) Remove the battery
2) Remove the charger
3) Push and hold the power button on for about 40 seconds - (it wont start as there is no power and you will look silly doing it, but do it anyway)
4) replace the battery
5) Switch it on like normal.
6) try the WiFI - if its not working now press the [F8] button.
Hopefully it will now be working and you might want to shower me in praise :^)
(if it doesnt work your not allowed to shower me in anything else!)
Let us know if this works.
I really appreciate thank you messages as a payment for solving issues :o)